Skip to main content

Full text of "The manufacture of lake pigments from artificial colours"

See other formats


THE MANUFACTURE OF 
LAKE PIGMENTS 

FROM 

ARTIFICIAL COLOURS 



Digitized by the Internet Archive 

in 2010 with funding from 

NCSU Libraries 



http://www.archive.org/details/manufactureoflakOOjenn 



PLATE IIa (Frontispiece) 



Manufacture of Lake Pigments 
Frontispiece 



See page 63 



THE MANUFACTURE OF 
LAKE PIGMENTS 

FROM 

ARTIFICIAL COLOURS 



FRANCIS H. JENNISON, F.I.C. 



SECOND REVISED EDITION 



WITH NINE PLATES 



LONDON 
SCOTT, GREENWOOD & SON 

8 BROADWAY, LUDGATE, E.C. 4 
1920 

[A II rights reserved] 

D. VAN NOSTRAND COMPANY 

S WARRKN ST., NEW YORX 



First Edition 1900 

Second Revised Edition .... January 1020 



PEEFACE. 

In revising the matter for this edition, it was con- 
sidered that it would be more in sequence if the 
section dealing with the sketch of the organic com- 
pounds at the beginning of the book in the pre- 
vious edition were transferred to the last chapter. 

There has been no deviation from the object of 
dealing with the chemical and physical problems 
which arise in the production of lake pigments in 
such a manner as to aid the lake-maker to devise 
his own methods and formuke, and avoiding, in so 
far as possible, definite recipes which may be good 
under one set of conditions but of no use in others. 

The production of lake pigments at the present 
time is very difficult, for, with the disappearance of 
the German dyestuffs from the market, there is great 
difficulty in obtaining reliable dyes that will pro- 
duce constant results ; for this reason the German 
names of dyestuffs have been retained in many 
instances, in order that those who are fortunate 
enough to have samples of these dyestuffs can 
readily compare them with what is now offered. 

Lake-making demands the bestpossible dyestuffs, 
for in most cases a lake when once formed cannot 



vi PREFACE. 



be altered, and irregular shades in various deliveries 
are ruinous to the reputation of the firm making 
them. The pigment trade is one of the largest 
users of dyestuffs ; it is to be strongly urged that 
the British dyestuff manufacturer will devote very 
serious attention to this important industry and 
regard it as equally important as the dyeing trade. 

I am deeply indebted to W. Davison, B.Sc, 
A. I.C.. and W. E. Merry, Esq., both of the Director- 
ate of Chemical Inspection, Royal Arsenal, Wool- 
wich, for their valuable assistance in reading and 
correcting the proofs. 

The British Dyestuffs Corporation (Hudders- 
field), Ltd., Huddersfield, have at great trouble 
and with much care been so good as to prepare 
the lakes and the plates for this edition, and I 
must make the most sincere acknowledgment and 
thanks for their help and kindness in this matter. 

F. H. JENNISON. 

Xewcastle-on-Tyxe, 
December, 1919. 



CONTENTS. 

CHAPTER I. 

PAGES 

Introduction 1-8 

CHAPTER II. 

The Classification of Artificial Colouring Matters 9-28 

CHAPTER III. 

The Nature and Manipulation of Artificial Colours 29-34 

CHAPTER IV. 

Lake-forming Bodies for Acid Colours . . . 35-45 

CHAPTER V. 

Lake-forming Bodies for Basic Colours . . . 46-51 

CHAPTER VI. 
Lake Bases 52-71 

CHAPTER VII. 

The Principles of Lake Formation .... 72-85 

CHAPTER VIII. 
Red Lakes 86-99 

CHAPTER IX. 

Orange, Yellow, Green, Blue, Violet, and Black 

Lakes 100-109 

CHAPTER X. 
The Production of Insoluble Azo Colours in the 

Form of Pigments 110-117 



viii CONTENTS. 

CHAPTER XL 

PAGES 

The General Properties of Lakes Produced from 

Artificial Colours 118-125 

CHAPTER XII. 
Striking. Washing, Filtering, and Finishing . . 126-133 

CHAPTER XIII. 
The Matching and Testing of Lake Pigments . . 134-146 

CHAPTER XIV. 
Sketch of Organic Combinations 147-164 

Index 165-172 



THE 

MANUFACTURE OF LAKE PIGMENTS 
FROM ARTIFICIAL COLOURS. 

CHAPTER I. 

INTRODUCTION. 

The generic term " lake colour " is applied to all pig- 
ments made from dyestuffs and colouring-matters, by 
precipitation of the colouring-matter as an insoluble 
compound, and serves to- distinguish such colours from 
natural pigments, such as ochre, umber, etc., and from 
chemical colours manufactured by direct combination or 
decomposition of distinct salts, e.g., such colours as lead 
chromates, Chinese blue, emerald green, etc. 

Prior to the introduction of the coal-tar dyes, lakes were 
made from the natural dyestuffs — cochineal, sapan wood, 
logwood, Lima wood, fustic, flavin, weld, etc. Many of 
these lakes are still in the market, and are known by such 
names as crimson lake, berry yellow, madder lake, Dutch 
pink, rose lake, leather lake, etc. ; but of recent years, ex- 
cept for some few and particular purposes, they have been 
superseded by lakes made from artificial colours, because 
the latter can be produced more easily and cheaply, and 
possess greater staining power, brilliancy, and constancy 
of shade. 

The application of colouring-matters to lake manu- 
facture is not without difficulty. Lakes intended for the 



•J THE MANUFACTURE OF LAKE PIGMENTS. 

preparation of linoleum colours, lithographic and ink pig- 
ments, paint grinding, and surface and wall papers, each 
have their own particular requirements, and the nature and 
properties of each pigment must be such as to render it 
suitable for the particular purpose for which it is required. 
Dyestuffs cannot be produced if there be not a definite 
known demand for them, and the closest co-operation be- 
tween lake makers and dye manufacturers is therefore 
essential, if success is to be assured. 

In the past the British dye firms have catered almost 
exclusively for the colour requirements of the textile 
trades, paying little attention to those of the pigment 
manufacturers, who readily obtained their supplies from 
abroad at prices generally lower than those ruling for 
home products. 

The closing of the continental source of dyestuffs 
greatly increased the difficulties of the lake manufacturer, 
for it was impossible for the British manufacturers to meet 
the increased demands of the textile trades and the new 
demand of the lake maker, since the particular require- 
ments of the latter were practically unknown to them. 
Their difficulties have been further increased by the fact 
that the greater part of their plant was urgently required 
for the production of explosives. 

It is, however, very important that the requirements of 
the lake trade be not overlooked. A little consideration 
will show that the consumpt of artificial dyes in the pro- 
duction of lake pigments is of very considerable magnitude, 
if not greater than that in any other industry. 

The technology of lake pigment making differs materi- 
ally from that of the dyeing trades. It is essential that 
the British and allied dyestuff manufacturers give very 
considerable attention to these requirements, and to the 



INTRODUCTION. 3 

peculiarities of the various branches of manufacture in 
which lake pigments form an important item. It is not 
unknown that the great German firms spared neither 
trouble nor expense to produce a particular colour to 
match not only the required shade but also particular 
properties required for some special purpose. They learned 
much of the technical .difficulties and requirements, not 
only of the lake makers but of the users of the pigments 
also. By this means they laid the foundation of their 
industry, gathering knowledge and information enabling 
them to deal with future difficulties of the same nature. 
They became cognizant of the weaknesses of the materials 
in use, and worked toward replacing them by very much 
superior articles. An example of this striving for more 
suitable materials is readily seen in the substitution of 
lithol reds for dyes of the eosine class; the latter were 
largely used for royal reds and vermilionettes. They were 
certainly very brilliant, their fastness to light being deplor- 
able. The introduction of the lithol reds very rapidly 
caused, save for some special purposes, the disappearance 
of this class of pigment from the market. The permanent 
and pigment reds have replaced the eosine vermilionettes ; 
because of the great permanency of the pigments from 
the newer class the demand for them has grown very con- 
siderably. 

The British dye firms, being hard pressed to meet the 
wants of the textile trades, and handicapped by necessary 
production of munitions, could not give much attention 
to this branch, but if some attention be not given in 
the near future, the lake manufacturers will be com- 
pelled to revert to those who, from accumulated know- 
ledge of their requirements, are ready to supply their 
particular needs. 



4 THE MANUFACTURE OF LAKE PIGMENTS. 

If the best and most economical results are to be 
secured in the manufacture of lakes from artificial dye- 
stuffs, and each lake is to be adapted correctly to the pur- 
pose for which it is required, some knowledge of the 
chemistry, constitution, and properties of the colours used 
is necessary. 

With the difficult and intricate chemistry of the pro- 
duction of the artificial dyestuffs the lake manufacturer 
need not be familiar, but a knowledge of the chemical 
nature of the colour he is using is essential ; e.g. , the reason 
why he cannot precipitate magenta with barium chloride 
when a scarlet is easily thrown down by this reagent re- 
quires his careful attention. A study of the constitution 
of colouring-matters will show that the nucleus of the 
molecule of any given colour is not, from the actual lake- 
producing point of view, the essential feature of the colour, 
the substitution and addition products of the chromophor 
are of vastly greater importance. For instance — 

Tropaolin 00 is phenyl-amido-azo-benzene sulphonic 
acid — 

HSO -C,H 4 N : N-C ti H 4 NHC, ; H, 

or C H f S °3 H 

" 4 \N : N-C (i H 4 NHC G H 5 

The chromophor of this colour is azo-benzene — 

C G H 5 -N : N-C (; H, 

From examination of the formula given, it is seen 
that in one of the benzenes of the diazo-benzene, one of 
the hydrogens has been substituted by the sulphonic acid 
group, and in the other by an amido-benzene. 

This being an acid colour, the latter substitution will 
be found to have no influence on the dyeing or lake-form- 
ing properties of the colour, but affects the colour of the 
dye by intensifying the shade, acting in this case only as 



INTBODUCTION. 5 

an auxochrome, as Witt names this property of certain 
organic radicles. 

The lake-forming properties of Tropaolin 00 depends 
only on the sulphonic-acid group present. 

The artificial colouring-matters are divided into several 
classes, according to the molecular configuration of the 
nuclei. 

The usual classification is — 

I. Nitro colours. 

II. Azo colours. 

III. Nitroso and isonitroso colour*. 

IV. Oxyketone colours. 

V. Ketonimides and hydrazides. 
VI. Triphenylamine colours. 
VII. Azines, oxazines, and thioazines. 
VIII. Quinoline colours. 
IX. Acridine colours. 
X. Sulpho colours. 

It is possible from a purely chemical aspect to increase 
this list very considerably, but, as the knowledge of the 
relations between the constitution and the chromatic pro- 
perties of the various groups is by no means perfect, and 
as the minor differences in the grouping of the molecules 
or radicles in the nuclei are of but little importance in the 
production of lakes, it would be of little profit to enter 
into the question very minutely. 

Before discussing the constitution of the colours in the 
various groups, an explanation of the terms used in de- 
scribing the several parts of a colour molecule, and of the 
various organic compounds and combinations which fre- 
quently occur in or compose the various dyestuffs, will be 
advantageous : — 



I) THE MAM'IACTUKE OF LAKE PIGMENTS. 

A chromophor group is the colour-giving group. 

A chromogen, a molecule containing only a chromophor. 

Salt-forming group, a group which imparts acid or basic 

properties to a colouring-matter. 
An auxochrome group, one which, though it may impart 

acid or basic properties to the colouring-matter. 

intensifies and alters the shade of the colour. 

An organic radicle is a group of atoms which go 

through a series of compounds without alteration, can 

be replaced in these compounds by a simple body, and, 

when combined with an element, such element may be 

substituted by some simple body. The methyl-radicle. 

CH 3 , when combined with hydrogen forms methane, CH 4 . 

which, when treated with iodine, gives iodo - methane, 

CH 4 + I 2 = CH 3 I + HI. Acting on iodo-methane with 

l f % H 
sodium, we get ethane, 2CH 3 I + Xa., = 2NaI + - p-rr H ; 

and this trydrocarbon, when treated with iodine, forms 
iodo-ethane, C 2 H 5 I. On the addition of ammonia, iodo- 
ethane forms ethylamine, C 2 H 6 I + NH 3 = C 2 H 5 NH 2 + HI ; 
when ethylamine is combined with nitrous acid it forms 
ethylamine nitrite, which, when heated, yields alcohol, 
C 6 H 5 NH 3 N0 2 = No + H 2 + C 2 H 5 OH. Oxidation of al- 

Alcohol. 

cohol gives acetic acid, CH 3 COOH, the sodium salt of which, 
when treated with caustic soda, yields methane. Thus ; 
CH 3 COONa + NaOH = CH 4 + NaoC0 3 , showing that 
after many changes the radicle, CH 3 , remains unaltered. 

In organic chemistry the compounds are divided into 
two series, the fatty and the aromatic, or the derivatives 
of methane and benzene ; it is from the latter that the dye- 
stuffs are derived, but the radicles of the methyl series 
take part as substituent groupings in many combinations 
of benzene nuclei. The nature of these combinations is 



INTRODUCTION. / 

dealt with in Chapter XIV., and is arranged in such a manner 
as, it is hoped, will afford a guide to the study of those com- 
hinations yielding dyestuffs from which lakes are produced. 

A survey of the whole problem of the manufacture of 
lake pigments from artificial colours resolves itself into three- 
main divisions, which may be summed up as follows : — 

(a) The study of the composition, and chemical and 
physical properties of the dyestuffs or colouring-matters, 
suitable for the preparation of lakes. 

(6) The chemistry of the reagents used, and the reactions 
and combinations which occur between these reagents and 
the colouring-matters in the production of lakes. 

(c) The nature and function of the base substrata or 
matrix, and its action on the nature and application of the 
resultant pigment. 

In the study of the chemistry of the dyestuffs, it will 
be seen that they are nearly all definite chemical com- 
pounds, some of a very complex character it is true, but 
still capable of fairly simple consideration from the point 
of view of their reactions ; and, from whatever source the}' 
may be obtained, the synonyms of both British and foreign 
manufacture are reasonably constant in their chemical 
composition and properties, though the actual strength 
and peculiar physical characteristics may show slight dif- 
ferences. Attention and careful study must be given not 
"• only to the chromophoric group and auxochromic groups, 
but to those radicles in the dyestuff which give to it the 
distinctive chemical properties of the class to which it 
belongs. 

The reagents used in the transformation of soluble 
dyestuffs into insoluble compounds, available for use as 
pigments, require careful study : they must be classified 
according to general properties, and the special character- 



S THE MANUFACTURE OF LAKE PIGMENTS. 

istics of the individual members of each group considered. 
In addition, when both basic and acid radicles occur in the 
molecule of a dyestufif, combination of two or more pre- 
cipitating agents may be necessary, and they must be so 
chosen as to secure the maximum result. 

Having decided the nature of the dye to be used, and 
the most suitable reagent or reagents for its precipitation, 
there still remains the question of the base on which the 
dye is to be precipitated. Almost invariably the suitability 
of a lake pigment for any particular application is governed 
by the nature of the base or matrix with which it is com- 
bined. Although lithol red precipitated on barytes would 
be satisfactory as a paint or linoleum pigment, it would 
be useless for lithographic work owing to the comparative 
coarseness of the matrix, and could be rendered suitable 
for the latter only by the substitution of blanc fixe — pre- 
cipitated barytes — for the coarse barytes employed. 

The function of the base is not one simply of loading 
or diluting a lake pigment. Apart from their physical con- 
dition being such as to render impossible the complete 
utilization of their tinctorial power, many of the lakes are 
useless in the pure state as pigments, owing to hardness 
and lack of body when dry. The base, therefore, must be 
regarded as an integral part of the lake pigment, and, as 
such, needs very careful discrimination in selection. The 
purpose for which the pigment is to be used must be in 
all cases the paramount guiding principle. 

It is with the practical application of the three branches 
of lake manufacture from artificial colours that it is pro- 
posed to deal in the following chapters. 



CHAPTER II. 

THE CLASSIFICATION OF THE ARTIFICIAL COLOURING- 
MATTERS. 

The Nitro Group. — The chromophor of this group is the 
nitro-radicle, NO.,, which, when combined with the amines 
and phenols of the aromatic series, produces dyestuffs of 
an acid character. The nitro-amido compounds, owing to 
the basic properties of the amido group, are of but little 
value, being of much less tinctorial power than those of 
the phenols. Only one sulphonic acid of this group of 
commercial value is in the market, namely, naphthol 
yellow S. The chief application of the colours of the nitro 
group in lake-making is to modify the shade of basic 
colours with which they combine, in some cases totally, 
but usually only partially precipitating them. The pre- 
cipitation of the basic colours by other means usually 
carries down the whole of the colouring-matter. Certain 
members combine partially with aluminium hydrate, 
Al 2 (OH) 6 , but, on heating and washing, the products are 
almost completely redissolved. Of the colours in this 
group those most generally met with are — 

OH 

Picric acid, C 6 H 2 OH(N0 2 ) 3 N( Y J N ° 2 ; napht hol yellow, and 

NO, 
naphthol yellow S. 

Naphthol yellow, dinitro-a-naphthol, C ]0 Hr,OH(NOo).,, 

(9) 



10 THE MANUFACTURE OF LAKE PIGMENTS. 

usually comes into commerce as the sodium salt, C 10 H 5 ONa 
(N0 2 ) 2 . Naphthol yellow S, the sulphonic acid of naphthol 
yellow, C 10 H 4 (OH)(NO 2 ) 2 SO 3 H, the sodium salt of which, 
C 10 H 4 ONa(NO 2 ) 2 SO 3 Na, is usually sold, combines with 
freshly precipitated aluminium-hydrate, partially forming 
a pale yellow lake. A more complete precipitation of the 
colour is secured, when the requisite quantity of barium 
chloride is used. In the presence of purely basic colours, 
naphthol yellow S is co-precipitated, but, after a time, 
separates out ; and the most complete precipitation is 
secured only when it is used in conjunction with amido- 
sulphonic-azo colours, and precipitated on a base in which 
there is freshly precipitated aluminium hydrate, by means 
of barium chloride. In these cases it evidently combines 
with the basic group of the colour used and with the 
aluminium hydrate, the complex giving, on the addition 
of barium chloride, a compound lake. Green lakes pre- 
pared in this manner are much faster to light than those 
produced by using other yellow dyestuffs. 

The Azo Group. — The azo dyestuffs are characterized 
by the fact that they contain the chromophor, — N = N — , 
linked up to two benzene rings or other aromatic hydro- 
carbons. They form several well-defined groups, which 
may be classified as follows : — 

(1) Amido-azo colours. 

(2) Oxy-azo colours. 

(3) Tetrazo dyestuffs. 

There are some other groups of minor importance, indi- 
vidual members of which are used in the preparation of 
lakes, but these can readily be considered in conjunction 
with the other groups to which they are related. 

Before proceeding to the detailed consideration of the 
azo colours, — by far the most numerous of artificial dye- 



CLASSIFICATION OF ARTIFICIAL COLOURING-MATTERS. 11 

stuffs,— it will be as well to discuss briefly their general 
formation, and the influence exercised on their colouring 
powers and properties, by the introduction of various 
hydrocarbons and their substitution products into the 
colour molecule. 

During recent years the azo-compounds have become 
of importance to the pigment maker, owing to the intro- 
duction of many dyes of this class into the market as pig- 
ment or permanent colours. The latter are simply azo 
colours of bright shades and great colouring power, which 
are frequently mixed with some substrata and sold as pig- 
ments. Some contain one sulphonic-acid group and are 
fixed or modified by the use of barium and calcium salts ; 
others are insoluble azo-compounds which are really pig- 
ments in themselves, but are not of much use in the arts 
as such, although they lend themselves readily to the pro- 
duction of useful pigments. On account of their great 
strength the so-called pigment and permanent colours can 
impart their shade to a high proportion of base or sub- 
strata. The nature and application of this class of artificial 
colouring-matter is dealt with fully in Chapter X. 

The highly coloured azo-compounds are not really 
dyestuffs unless they contain some body imparting acid 
or basic properties. For instance, azo-benzene, though 
a brilliantly coloured body, does not possess dyeing pro- 
perties until it is sulphonated, i.e., converted into the 
sulphonic acid of azo-benzene, when it acquires tinctorial 
powers, which, however, are considerably increased by the 
introduction of an auxochrome group like (OH). The 
introduction of the amido-radicle confers basic properties 
on the compound ; and, whereas the acid azo-compounds 
have to be sulphonated to render them soluble, the basic 
are usually so without further treatment. They combine 



12 THE MAHUFACTUBB OF LAKE PIGMENTS. 

with acids, however, to form salts. The introduction of the 
various auxochrome groups exercises great influence on the 
colour produced, more especially if they be of an entirely 
different nature from those constituting the parent colour. 

The compounds which contain only hydrocarbons of 
the benzene series are yellow, orange, and brown. The 
introduction of naphthalene changes the colour to red ; 
and, as the number of naphthalene rings increases, they 
become bluer, yielding violets and various shades of blue 

The Amido-azo Colours. — The amido-azo colours are of 
a basic nature. Some members of this section come into 
commerce as sulphonic acids although the majority are 
simply the amido-derivatives. Though both the amido- 
and sulphonic-acid groups confer certain properties on the 
colour molecule, the one being basic and the other acid in 
nature, it is only w T hen these two opposite characteristics 
are satisfied that the best results can be looked for. 

To attempt to give a detailed list of the colours of this 
division alone would be of little value, since there are many 
such lists already in existence. 1 As a general rule they 
can be regarded as members of the same family, answering 
to the same reactions in respect of precipitation and lake- 
forming. It is proposed to deal with the chief represen- 
tatives only : — 

Chrysoidine : diamido-azo-benzene, C,H 4 X : N'C 6 H^(NH 2 ) a 
Diphenylamine Orange or Acid Yellow D : sodium salt of 
p.-sulphobenzene-azo-diphenylamine. 

f(4)SO,Na 



V)N:N-(l)C i; H 4 (4)NH-C,H, 



A very good work of reference dealing with the constitution, formula, 
and properties of the artificial colours is Schultze and Julius' Tlie Systematic 
Survey of the Organic Colouring Matters (last edition, 1914). 



CLASSIFICATION OF ARTIFICIAL COIiOURING-MATTERS. L3 

Metanil Yellow : the sodium salt of meta-sulphobenzene-azo- 
diphenylamine, 

f(3)S0 3 Na 
C H J 

4 [(1)N:N(1)C,H 4 (4)NH-C H, 

Acid Brown R : salt of p.-sulphonaphthalene-azo-phenylene 
diamine-azo-benzene, 

c R f (4)S0 3 Na 
°i''N(l)N:N\ r R ((1)NE, 
C H,-N:N/^ i±1 n(3)NH: 

Bismarck Brown : hydrochloride of benzene disazo-phenyl- 
enediamine, 

f(l)N:N-(l)C 6 H 8 ] 

°e*M ((2)NH.,-HC1 

(3)N:N-(l)C,H a 

When sulphonic-acid groups are absent from the colour 
molecule, the colouring-matter can be thrown down as a 
lake by those means usually adopted for purely basic 
colours, e.g., by combination with tartar emetic and tannic 
acid. 

When the sulphonic-acid group is present, barium 
chloride precipitates the bulk of the colour in most cases, 
but the precipitation is usually not complete. The ad- 
dition of a little oleic acid, previous to the addition of the 
barium chloride, renders the precipitation more complete, 
and greatly increases the fastness and brilliancy of the 
lake produced. This is very noticeable in the case of 
metanil yellow. 

The Oxy-azo Colours. — The most important members 
of this group are the derivatives of the isomeric naphthols 
and their sulphonic acids. Of the colours derived from 



14 THE MANUFACTURE OF LAKE PIGMENTS. 

benzene, the most important is Tropaolin 0, or Eesorcin 
Yellow : the sodium salt of p.-sulphobenzene-azo-resorcinol, 
f(4)S0 3 Na 
4 1(1)N:N;4)C 6 H 3 { ( ( ^H 

The naphthol-azo dyes are almost entirely used in the 
form ofi sulphonic acids. The sulpho group has very little 
influence on the shade, but the different isomeric naphthol- 
sulphonic acids give entirely different shades with the same 
diazotized base. The derivatives of /3-naphthol are found 
to be more permanent than those of a-naphthol, owing no 
doubt to the method of arrangement of the various sub- 
stitution groups in the naphthalene ring. 

When the naphthol-sulphonic acids are combined with 
the diazo-compounds of benzene, yellow and orange colours 
are produced ; with the higher homologues the colours 
become red ; and with the derivatives of naphthalene we 
have again reds, which become more blue with increasing 
molecular weight of the compounds. The colours known 
as the coccinines are derived from diazoanisol and its 
homologues and /3-naphthol disulphonic acid. 

The oxy-azo colours are very numerous, and vary in 
colour from yellow to deep bluish-red. Of those which 
demonstrate the constitution of this group the following 
examples are given : — 

Orange 2. — Sodium salt of p.- sulphobenzene - azo - /3-naph- 
thol, 

f(l)S0 8 Na 
C "FT ' 

4 [(4)N:N(1)C 10 H 6 (2)OH 

Mandarin G. R. — Sodium salt of sulpho-o.-toluene-azo-/3- 

naphthol , 

f(2)CH 3 

t(l)-N:N(l)C 10 H t ;OH(2) 



CLASSIFICATION OF ARTIFICIAL COLOURING-MATTERS. 15 

Ponceau 2 G. — Sodium salt of benzene-azo-/?-naphthol di- 
sulphonic acid, 

f(2)OH 
C 6 H 6 N : N-(1)C 10 H 4 (3)S0 3 Na 
((6)S0 3 Na 

Ponceau 3 R. — Sodium salt of ^ cumine-azo-/3-naphthol di- 
sulphonic acid, 



C 6 H* 



f(5)CH, 
(4)CH 3 

(l) )C N H3 N-C 1(( H 4 {^ Na)) 



Ponceau 2 E. — Sodium salt of xylene-azo-/3-naphthol di- 
sulphonic acid, 

f(2)OH 
C i; H 3 (CH 3 ) 2 -N : N-(1)C 10 H 4 (3)S0 3 Na 

((6)S0 3 Na 

Fast RedB, or Bordeaux B. — Sodium salt 1 of a-naphthalene- 
azo-/?-naphthol disulphonic acid, 

f(2)OH 

C 10 H 7 (a)N : N-C 10 H J (3)S0 3 Na 
\(6)S0 3 Na 

Croceine Scarlet B. X. — Sodium salt of sulphonaphthalene- 
azo-/3-naphthol monosulphonic acid, 

H |(4)S0 3 Na QH 

° 10 4(1)N : N-(2)C 10 H 5 {^ Na 

The Tetrazo Dyestuffs— The tetrazo or disazo colour- 
ing-matters are of a much more complex nature, and 
differ from the azo colours in that they contain the 
chromogen \N : N" more than once in thejmolecule. They 
may be divided into three classes : — 

(a) Those which contain two azo groups and the auxoehrome 
groups in one benzene nucleus, e.g., phenol-disazo-benzene, 

C S H 5 'N:N'CA{2 H N . CA 



16 THE MANUFACTURE OF LAKE PIGMENTS. 

(b) Those which contain the disazo groups in one ring and 
the auxochromes in the others. Tetrazo-benzene-phenol, 

C t .H 5 -N : N-C.H.-N : N-C„H 4 OH 

(c) The disazo dyestuffs derived from benzidine, 

C 6 H 4 -NH„ 

I 
C,.,H 4 'NH 2 and its homologues. 

Without entering into minute details concerning the 
formation and the chemical peculiarities of each of these 
groups, their general formation may be represented by 
the following few examples of this extremely numerous 
class : — 

Biebrich Scarlet. — Sodium salt of sulphobenzene-azo-sulpho- 
benzene-azo-/?-naphthol, 

CH r(4)S0 3 Na , S0N 

Ponceau 4 E. B. — Sodium salt of sulphobenzene-azo-ben- 
zene-/?-naphthol-monosulphonic acid, 

C ^{(4)N :N a C 6 H 4 -N : N-(l)C, () H 5 { ( ^^ Na 

Bordeaux G. — Sodium salt of sulphotoluene-azo-toluene- 
azo-/^-naphthol-/?-sulphonic acid, 

[N : N-C 6 H 3 1^. (1 c H ((2)OH 

Naphthol Black 6 B. — Sodium salt of disulphonaphthalene- 
azo-a-naphthalene-azo-y8-naphthoL disulphonic acid, 

f(S0 3 Na) 2 f(2)OH 

c i«» H fi(N : N-(4)C 10 H (1)N : N-(1)C 10 H 4 J (3)S0 3 Na 

[(6)S0 3 Na 

Acid Brown G. — Sodium salt of benzene-azo-phenylene 
diamine-azo-benzene-p.-sulphonic acid, 

(NH 2 
C,H,N : N-C 6 H 2 J NH." 

" N : N-(l)C,H 4 (4)S0 3 Na 



CLASSIFICATION OF ARTIFICIAL COLOTJBING-MATTBBS. 17 

Cloth Brown G. — Sodium salt of diphenyl-disazo-dioxy- 
naphthalene-salicylic acid, 

(l)C,H 4 (4)N:N-C ( ft(}^ OH 

(1)C H 4 (4)N:N— (1)C 10 H 5 {[2)OH 

Diamine Fast Bed. — Sodium salt of diphenyl-disazo-sali- 
cvlic-amido-naphthol-sulphonic acid, 

|(2)NH 2 

(V,H t (4)-N:N-C l() H '(8)OH 
(1) | [(6)S0 8 Na 

W ).N:NC,ft{S Na 

lirnzopurpurine 4 B. — Sodium salt of ditolyl-disazo-binaph- 
thionic acid, 

(3)CH 3 c H f(l)NH 2 

W I „ (4)-N : N-(2) c „ f(l)NH 2 

Closely related to the tetrazo colours are the derivatives 
of the thiotoluidines, of which the following two members 
are the most important : — 

Primuline is a mixture of which the chief constituent is 

( j ! \ N / C « H »' C \ N /' C fi H 8 ,CH 3 

/Sv /S0 3 Na 

C,!H3 \ N ^ C ' CA \ NH:i 
Thioflavin-dimethyl-dih\drothiotoluidene-methyl chloride. 
GH 8 C1 

C 6 H 8 (4)C 6 H 8 <((1)^C(4)C 6 H 4 (1)N(CH 3 ) 2 

S X 
(2) 

The precipitation of the members of this section is 

usually effected by the agency of barium chloride, which 

2 



Is THE MANUFACTURE OF LAKE PIGMENTS. 

tonus the insoluble barium salt of the compound. In 
many cases, however, the number of lake-forming groups, 
in addition to the sulphonic-acid groups, renders it neces- 
sary to use further reagents to effect the complete precipi- 
tation of the colour, and to increase its fastness and 
brilliancy. This, and the formation of a series of pigments 
of growing importance, viz., the production of insoluble 
azo colours on suitable bases, will be more fully considered 
later. 

Nitroso and Iso-nitroso Colours. — These form an un- 
important group, from which lakes are rarely made. They 
contain the chromogen 'NOH. About the best-known 
member is Gambine, /3-nitroso a-naphthol 

( (1) CO— C = NOH 
C (i H 4 | 

i(2) CH = CH 

Oxyketone Colours. — The oxyketone group is one of 
the most important, as it embraces the alizarines and 
allied colours, containing the powerful acid-forming 
chromogen, : CO, which, when acid-forming auxochromes 
are introduced into the molecule, gives powerful colouring- 
matters. These colours have, however, to be united to 
metallic oxides, before their full colouring power and 
shade are developed. 

The derivatives of benzene and naphthalene are known, 
but they are of much less importance than those of an- 
thracene, the principal colouring-matters derived from this 
hydrocarbon being — 

Alizarine VI. — a-/3-dihydroxy-anthraquinone, 

r „ /CO\ r H OH (6) 

^^XCO/^'' -'OH (5) 

Alizarine EG. — Trihydroxy-anthraquinone, 
(4) HOC (i H 3XCO/ C,H 20H w 



CLASSIFICATION OF ARTIFICIAL COLOURING-MATTERS. 19 

Purpurin. — Trihydroxy-anthraquinone, 

'\CO/ \OH(5) 
Alizarine Bordeaux. — Tetrahydroxy-anthraquinone, 
OH o OH 

0-1=0°" 

HO 
Alizarine Orange. — Nitro-alizarine, 

/co\ r 0H (6 ^ 

xuu/ <- N 2 (4) 

Alizarine WS. — Sodium salt of alizarine-monosulphonic- 
acid, 

/co\ f 0H (6 ) 

xuu/ [S0 3 Na 
Alizarine Blue. — Dihydroxy-anthraquinone-quinoline, 

C ^\CO/ C ^ OH )2\ " I 
x ^ u/ (6, 5) X CH = CH 

Alizarine Indigo Blue. — The sodium bisulphite compound of 
pentahydroxy-anthraquinone-quinoline. 

Great care has to be exercised in making lakes from 
these colours. The aluminium lakes are usually those 
prepared, and the author has found the following general 
method of procedure yield the most satisfactory results 
as regards brilliancy of shade : — 

Dissolve the alizarine in a mixture of carbonate and 
phosphate of soda, add the requisite quantity of oil, and 
carefully precipitate in the cold with sulphate of alu- 
minium ; add the calculated amount of acetate of calcium, 
and develop the shade by slowly raising to the boil in 
the course of about three hours, and boil one hour. 

The reasons for this procedure will be fully explained 



20 THE MANUFACTURE OF LAKE PIGMENTS. 

when dealing with the precipitation of colours, since there 
are many points into which it would be inadvisable to go 
fully at this stage. 

This method is also applicable to colours which are not 
alizarines, but, though belonging to other groups, are ad- 
jective colours. 

Ketonimides and Hydrazides. — The ketonimides and 
the hydrazides are allied to the oxyketones, but only one 
colour of each group is at present of any interest to lake 
manufacturers, namely, Auramine, a valuable yellow basic 
dyestuff of great value in the production of green lakes 
from basic colours, and Tartrazine. 

The chromophor of Auramine is HN : C, and the generally 
accepted formula HN : C^Si'^'SKS^HCl 

This colour is precipitated with tartar emetic and 
tannic acid, as well as by the other methods used in the 
precipitation of basic colours ; and finds its greatest use in 
lake-making as an agent for modifying the tones of the 
more powerful triphenylamine colours. 

The hydrazine colour, Tartrazine, is the sodium salt of 
benzene azo pyrazaline-carboxy-disulphonic acid, 

.N = C— COOH 
C H 4 (SO 3 Na)-N< | 

x CO— CH— No— C (i H 4 (S0 3 Na) 

It precipitates completely with barium chloride, yielding, 
especially on a base of aluminium hydrate, a bright golden 
yellow lake ; but, since cheaper colours give a very similar 
shade, it is not much used, though its lake is fairly fast. 

Triphenylamine Colours. — In this group occur nearly all 
the basic artificial colouring-matters. They are usually very 
soluble, and of great colouring power, and, owing to the 
brilliant shades they produce, are largely used in the pro- 



CLASSIFICATION OF ARTIFICIAL COLOUBING-MATTEBS. '21 

duction of lakes. They are, however, as a general rule, 
extremely fugitive to light, but their brilliancy causes them 
to be more in demand than faster colours which are duller 
in shade. 

Like the azo colours, they can be divided into three 
classes : — 

(a) The rosaniline dyestuffs, containing the chromogen 
=C— NH— 

(b) The rosolic acid dyestuffs, containing the chromogen 
=C— O— 

II 

(c) The phthaleins, containing the chromogen C 

The following will be found to be representative mem- 
bers of the rosaniline dyestuffs : — 

Malachite Green. — Zinc double chloride of tetramethyl-p.- 
amidotriphenylcarbinol, 

C H _ C /(^^^W{Cn,), 

^\(l)C tJ H 4 (4)N-(CH 3 ),Cl 



Brilliant Green. — Sulphate of tetraethyl-diamido-triphenvl- 
carbinol, 

c h V^WWW 

"\(1)C 6 H 4 (4)N-(C 2 H 5 ) 2 



Acid Green. — Sodium salt dimethyl-dibenzyl-diamido-tri- 
phenylcarbinol-trisulphonic acid, 

/(l)C 6 H 4 (4)N(CH 3 )CH 2 -C i; H 4 S0 3 Na 
HOC— C H 4 -SO,Na 

\(l)C H 4 (4)N(CH 3 )CH,-C,H 4 SO 3 Na 

Guinea Green B. — Sodium salt of diethyl-dibenzyl-diamido- 
triphenylcarbinol-disulphonic acid. 



22 THE MANUFACTURE OF LAKE PIGMENTS. 

Night Blue. — Hydrochloride of p.-tolyltetraethyl-triamido- 
diphenyl-a-naphthylcarhinol, 

/C H 4 N(C. 2 H 5 ) 2 
C-C ti H 4 N(C,H 5 ) 2 
\C 10 H 6 N : (C 7 H 7 )HC1 

Magenta. — The various brands of this colour are mixtures 
of the various salts of rosaniline and pararosaniline. The 
hydrochlorides may be expressed thus — 

/(l)C ti H 4 NH 2 (4) /^ n *(4)NH 2 

C— (1)C (J H 4 NH 2 (4) and C— C H 4 NH 2 (4) 
I \(1)C, ; H 4 NH 2 C1 (4) \C H 4 NH 2 C1(4) 



Alkali Blue D. — Sodium salt of triphenyl-pararosaniline 
monosulphonic acid, 

/(1)C 6 H 4 (4)NHC 6 H 5 

C— (1)C,.H 4 (4)NHC,H 5 
\(l)C 6 H 4 (4)NHC H 4 SO 3 Na 

Methyl Blue C. — Sodium salt of triphenyl-pararosaniline 
trisulphonic acid, 

/(l)C (; H 4 (4)NH-C H 4 -SO 3 Na 

HO— C— (l)C ti H 4 (4)NH-C,H 4 -S0 2 Na 

\(l)C 6 H 4 (4)NH-C t; H 4 -S0 3 Na 

The basic dyestuffs of this group lend themselves 
to precipitation by various acids, such as tannic, oleic, 
phosphoric, and arsenious acids, producing lakes of varying 
stability and brilliancy. The most permanent are those 
produced from tannic acid, but they are far from being 
so brilliant, especially in the case of the magenta and green 
colours, as those produced by arsenious and oleic acids. 
The violets give the best results with phosphoric acid, 
which will not take down at all many of the blues and 
greens. Very good shades are produced with tannic acid 
from the blues and the bluish-greens. 

Where the sulphonic-acid groups are not numerous, 



CLASSIFICATION OF ARTIFICIAL COLOURING-MATTERS. 23 

the colour can often be treated as a purely basic one; but 
where they are numerous, means have to be taken, which 
will be more fully dealt with in a later chapter, to pro- 
duce the double lakes. 

Many of the acid colours, such as acid magenta, are of 
but little value to lake-makers, it being almost impossible 
to precipitate them suitably. 

The colours from rosolic acid are not of very much im- 
portance, the chief representatives being — 

Aurine or rosolic acid, 

/(l)C 6 H 4 OH (4) 

C-(l)C t; H 4 OH (4) 

\(1)C,H 4 (4) 



and Chrome Violet — sodium salt of aurine tricarboxylic 
acid, 

(l)C,H aC00X , i 

HO-C-(l)C,,H^ ONa 
\ rH OH 

neither of which rind any employment in the production 
of lakes. 

The phthalein colours, however, contain a very impor- 
tant class of colouring-matters, namely, the eosines, which, 
together with the basic colours derived from this group, 
the rhodamines, give a number of colours which yield 
lakes of the brightest and most brilliant shades. The 
general formula of the principal members may be repre- 
sented by the following examples : — 

Eosine A. — Alkali salts of tetrabrom-rluoresee'ine, 

(4) : C,.HBr./^C, ; HBroONa(4) 
C i; H 4 COOXa 



•24 THE MAX! FACTUBB OF LAKE PIGMBJNTS. 

Erythrosine. — Alkali salts of tetraiodo-fiuoresceine, 

(4) : C, ; HI 2 ^\c tl HI 2 ONa (4) 

I 
C,H 4 COONa 

Phloxin. — Alkali salts of tetrabromdichlor-rluoresceine, 
(4) : C,HBr/°\c,HBr 2 ONa (4) 

C t; H 2 Cl 2 COOXa 
Rose Bengal. — Alkaline salts of tetraiododichlor-fluoresceine, 

(4) : C 6 HI /g\0 6 HI s 0Na (4) 

C, ; H 2 Cl 2 COONa 

Rhodamine B. — Hydrochloride of diethyl m. amido-phenol- 
phthalein, 

(C 2 H 5 ) 2 N(4)C 6 H 3 / \C 6 H 3 (4)N(C 2 H 5 ) 3 HC1 

/\ 

\ 

/ \ 

O = C C G H 4 

Rhodamine S. — Hydrochloride of dimethyl m. amido-phenol- 
succineine, 

(CH 3 ) 2 N(4)C (i H/ )C (i H 3 (4)N(CH 3 ) 2 HCl 

/ 
O 

/ 
O : C C 2 H 4 

Other higher products of this group, such as Galleme 
and Coeruleine, are of more interest to the dyer, producing 
violet and green shades on mordanted goods, but are rarely 
used in lake-making. 

Azines, Oxazines, and Thioazines. — The oxazine, thio- 
azine. and azine colours are the derivatives of a rather 



CLASSIFICATION OF ARTIFICIAL COLOUBING-MATTEBS. 25 

complex chromophor, which, in the case of the oxazines, 
may be shown as follows : — 



N 



\0/ 



the thio- or sulphur-azines, as 



and the azines, as { ). In the safranines the latter become 
modified thus, S ). This group contains a number of 



extremely valuable colouring-matters, mostly of a basic 
character, which give very useful lakes, the principal being — 
Fast Blue 2 B. — Chloride of dimethyl-phenyl-ammonium-/?- 
naphthoxazine, 



Cl(CH 3 ) 2 NC (! H 3 ^\ CioH(; 
Nile Blue A. — Chloride of dimethyl-phenyl-ammonium-a- 

amido-/?-naphthoxazine, C1(CH ; j) 2 NC,. > H 3 < / q")C 10 H 5 NH ; , 

Methylene-Blue B.— Chlorides of tetramethyl thionine, 

/N(CH 3 ) a 

NC >S 



^6-"-"-8\ 

N(CH 3 ) 2 C1 



^C ti H 3 < 



New Methylene-Blue. — Chloride of diethyl-toluthionine, 



/N\ nTT/ /CH s 



ClH(C 2 H 5 )-N-C fl H 2 /-^C 6 H 2 /--3 C3Hs 



THE MANUFACTURE OF LAKE PIGME1 

Of the azines, the safranines are of the greatest im 
The indulines. though yielding lakes, are not much used 
by the lake-makers, since the shades produced are lacking 
in brilliancy, and can more readily be obtained from other 
colours. 

The general formation of the safranine group will be 
understood from the following examples. These colours 
are basic in nature, and give very good results with tartar 
emetic and tannic acid. 

S nanine B. — Diamido-phenyl-phenazonium chloride. 

H^T,H 3 <J V.HXEL 

X\ 
CIC.H. 

Basle Blue R. — Dimethyl-amido-tolylamido-tolylphenon- 
naphthazarine chloride. 

N 

XCH C H.XHC : H : 

X N 



C1C-H- 

Mttaphenylene - Blue. — Tetramethvl - diamido - o. - tolyl - di- 
phenyl-azoniurn chloride, 

C1C-H- -H- 

\/ 

N N 

I N X / | 

N I H 

The tannic acid lakes of these colours are the best. 
The blues yield fine shades ; the red shades yield brighter 
and faster lakes than those produced from magenta, and 
are of great use in the production of bright maroon lakes, 
as they have not the same tendency to darken. The 
-juinoline and acridine colours are principally of inter- 



CLASSIFICATION OF ARTIFICIAL COLOURING-MATTBBS. 27 

est because they yield us Quinoline Yellow aud the 

/\CH = CH 
Phosphines. Quinoline, C H 7 N, | and acridine, 

\J— N = CH 

C«H 4 v \C fi H 4 , are the chromophoric groups ; but their 

power is but feeble, and only becomes of value when 

powerful auxochrome groups are introduced. 

Quinoline Yellow is the disulphonic acid of quinoph- 

thalone, 

r /CH-C lJ H 4 N(S0 3 Na). ( 
7\C,.H 4 — CO-0 ' 



and is entirely precipitated by barium chloride. 

The acridine colours are basic. The Phosphines are 
used for tinting purposes, but do not by themselves give 
pleasing lakes ; both tannic acid and resin soap take them 
down, the latter giving the brighter shades. By reference 
to the formula of Phosphine, nitrate of diamido-phenyl- 
acridine, 

C 6 H 4 NH„ 
I 

c.h 4 ( | Xh,nh 3 .hno, 

their general constitution can easily be understood. 

Of recent progress in the dye industry, the introduction 
of the azo colours and the development of the vat dyes 
are of interest to the pigment-maker. Sulpho and indo- 
anthene colours are not of great value to commercial lake 
manufacturers, for, though they can be applied, the dull- 
ness of the resulting lakes prevents their adoption in place 
of much brighter shades, whose durability is sufficient 
for the purpose for which they are manufactured. Some of 
these colours have, however, replaced the more fugitive 



28 THE MANUFACTUBE OF LAKE PIGMENTS. 

basic dyes in stencil inks and other similar spirit prepara- 
tions. 

Of the groups of artificial colours those described will 
be found to contain the colours most generally used in 
the production of lakes. Those which have been dealt 
with but slightly contain many valuable colours, but they 
are of more interest to the dyer and colour-maker, being 
only very occasionally applied to the production of pig- 
ments. It is for the latter reason that many groups have 
been omitted entirely, and not because they are considered 
unimportant. 



CHAPTEK III. 

THE NATURE AND MANIPULATION OF ARTIFICIAL COLOURS. 

The colours derived from coal-tar come into the market 
in three forms, namely — 

I. Amorphous powders. 
II. Crystals. 
III. Pastes. 
By far the greater number are sold as amorphous powders. 
The crystalline variety are mainly basic colours, such as 
magenta, ethyl-green crystals, violet crystals, etc., and can 
generally be regarded as almost pure derivatives of the 
dyes. 

The colours which are sold as powders are often 
diluted with from 10 per cent, to 80 per cent, of soluble 
matter, such as dextrin, common salt, Glauber's salts, and 
similar bodies. There are several reasons for this adultera- 
tion, the chief being the reduction of the strength of the 
colour, so that larger quantities of the dyestuff can be used 
and the approximation of the price to that of competing 
colours. By this means the danger of a slight error in 
weight causing a considerable alteration in the shade of a 
pigment is avoided. These colours, it must be remembered, 
are produced and prepared for the market for the use of 
dyers and printers, and the adulterants added may, for 
many reasons, render the colours more suitable for use in 
the dye-house ; but, when used for the production of lake 
pigments, by entering into one or more of the reactions 

(29) 



30 THE MANUFACTURE OF LAKE PIGMENTS. 

taking place in the formation of the lake, they may lead to 
results that are not expected, and may cause a colour, 
otherwise admirably adapted for this purpose, to be con- 
demned. It is therefore advisable, wherever practicable, 
" to obtain as pure a colouring-matter as possible. The 
lake-maker makes use only of the tinctorial power of the 
colours, diluting the shade produced, by means of bases, 
to the depth and strength required, and the presence of 
diluents, if they enter into any reaction during the lake- 
forming process, leads not only to misleading results but 
actually increases the cost of production. The purer 
brands of dyestuffs are often distinguished by the term 
extra, and though the price of the latter may be from six 
to ten times the price of the ordinary brand, it will be 
found that value for value the purer form works out much 
the cheaper in practice. 

The paste colours as a rule are those insoluble or 
nearly insoluble in water, e.g., the various alizarines or 
pigment colours, Lithol Eed K, Lake Red P, etc. They 
usually contain 20 per cent, of colouring-matter. In many, 
but not all instances, colours so supplied can be obtained 
almost pure in powder form, and it is better for the reasons 
already stated to use the latter where possible. With the 
colours of the azo group, however, and especially with those 
which require no addition to bring up the shade, but are 
simply ground or mixed with the base or filler, better re- 
sults are obtained by using them in paste form since the 
colour is then more readily and intimately mixed with the 
substrata. The lake-maker must discriminate in these 
cases as to which form will prove most economical in use. 

In selecting colours it is advisable to buy only from 
the actual makers or their immediate agents, avoiding 
as far as possible merchants and dealers. The colours 



NVTI'HI-: \X1> MANIPULATION OF ARTIFICIAL COLOURS. :'>1 

obtained from the latter cannot be relied upon to be constant 
in composition or purity ; and should any cause for com- 
plaint arise it would be impossible to have it investigated 
by the dye manufacturer, since he cannot be responsible 
for what may have happened to his products whilst passing 
through various hands after leaving his factory. 

It is not possible in the present condition of the dye 
industry to particularize the most suitable products of these 
firms. Many of them are handicapped by the prevailing 
conditions, and have not had the time and opportunity to 
develop the colours used in lake-making on the lines 
they would wish. It is, however, to be hoped that these 
products will be given every opportunity of replacing the 
continental colours. The lake manufacturer should not 
hesitate to point out any defects and to request the dye- 
stuff-makers to correct, if possible, those properties of 
their dyestuffs which render them inferior to those obtained 
from the previous sources of supply. It is to be feared 
that for a little time the greatest consideration will be 
necessary on both sides, before the products of the com- 
paratively new British dye industry can be accepted with 
the same reliance as were those of the great German dye 
manufacturing companies. But there is no reason why 
in a comparatively short time the British products should 
not inspire confidence as great as, if not greater than, 
those previously obtained from Germany. 

In the case of many of the colours made by the British 
firms before the war, there is no doubt that the shades had 
not the brilliancy of the same material made abroad. This 
would not have been so fatal to the use of the British colour, 
had not the price been almost without exception, higher, 
and in keenly cut prices the lake manufacturer could not 
afford to pay the higher cost. 



32 THE MANUFACTURE OF LAKE PIGMENTS. 

The suitability of a dyestuff for its application to textile 
fabrics is no criterion of its suitability for lake-making. 
and it is only by repeated trials and experiments that the 
value of a dyestuff for the latter purpose can be deter- 
mined. 

When colours are offered which do not bear the name 
of a recognized firm, they must always be looked upon with 
a certain amount of suspicion, since they are often sophisti- 
cated colours prepared for a special purpose, and, as such, 
are of questionable value in lake-making. It is certain 
that there will be on the market many dyestuffs from small 
and experimenting firms at rates much lower than these 
obtaining for established brands, and, while these may 
be used for odd lots of lake pigments, it would not be ad- 
visable for a lake-maker to attempt to prepare his standard 
shades and products from them. Great care and discretion 
will have to be employed in their use. 

Colours should always be dissolved in water separately. 
and then sieved into the precipitating tank through a fine 
-ieve, about eighty meshes to the inch. The wooden vessels 
in which acid and basic colours are dissolved should not 
be used for either class of dyestuff, since if the strong 
basic colours come into contact, even in minute quantities, 
with acid colouring-matters, they frequently alter materi- 
ally the shade of the finished lake, or, worse still, produce 
•lark tarry specks throughout the pigment, absolutely ruin- 
ing it for all ordinary processes. 

Where a mixture of similar colours is being used, it 
will be found that if the colours are dissolved and added 
separately to the tank, a different shade is produced from 
that obtained when all the colours are mixed together 
before addition. In the case of azo-acid colours, the latter 
is the more correct procedure, but with basic dyes it is. as 



Manufacture of Lake Pigments 



To face page 32 



NATUEE AND MANIPULATION OF ARTIFICIAL COLOURS. 33 

a rule, preferable to adhere to the former since, should one 
member of a mixture contain an acid group, another will 
frequently react with it, producing a tarry precipitate with 
which it is difficult to deal. 

Plate I illustrates some of these points : — 

(1) Shows the lake produced from Scarlet E (Brit. Dyes) on 
the clay alumina base by barium chloride. 

(2) A similar lake produced from Orange WH (Brit. Dyes). 

(3) A similar lake produced from a mixture of equal parts of 
Scarlet E (B.D.) and Orange WH (B.D.) dissolved together. 

(4) A similar lake to No. 3, but the dyestuffs dissolved separ- 
ately. 

(5) A lake produced on the clay alumina base by dissolving 
and adding separately Scarlet E (B.D.) and Magenta Crystals 
(B.D.), and precipitating the whole with barium chloride. 

(6) The same lake as No. 5 but the Scarlet E and Magenta 
dissolved together. 

In the majority of cases the best mode of dissolving the 
artificial colours is to make them into a thin cream with 
just warm water, and then add boiling water until the colour 
is entirely dissolved. Though boiling the colours does not 
usually injure them, it is better avoided, since, in some 
cases, notably in that of auramine, the colour is decom- 
posed, giving quite a different shade from that expected. 

In the case of colours obtained in the crystalline form 
a slightly different procedure is advisable, viz., to add them 
little by little to a considerable quantity of nearly boiling 
water, in the proportion, say, of half a pound of colour 
to 2 gallons of water, agitating until solution is complete. 

Except in the case of difficultly soluble colours, the 

addition of soda or other materials to the water, in order 

to facilitate solution, is to be strongly deprecated, since 

such additions are the cause of difficulties which would 

3 



34 THE MANUFACTURE OP LAKE PIGMENTS. 

otherwise be avoided. In such cases, however, the addi- 
tion of a little glycerine to the dyestuff when making it 
into a cream with water greatly increases the solubility. 
An equally effective but cheaper aid to solution is a small 
quantity of neutral Turkey Red Oil. Care, however, is 
required in using this, for, if in the subsequent manufac- 
turing operations there be any considerable effervescence, 
a> when soda ash is added to aluminium sulphate, the 
mixture will froth excessively, thereby lengthening the 
sticking time, and .giving much unnecessary work and 
trouble. 



CHAPTEE IV. 

LAKE-FORMING BODIES FOR ACID COLOURS. 

Having considered the general constitution of the artificial 
colouring-matters, it is advisable to enter into the chem- 
istry and nature of those reagents commonly used in the 
commercial production of lake pigments. There are many 
methods, extremely interesting from a scientific point of 
view, of forming lakes ; but attempts to reduce them to 
practice fail, because either they are too expensive, or the 
results are not of sufficient value to induce deviation from 
more general methods. 

The principal materials used in the preparation of lakes 
from acid dyes are the salts of — 

Barium — the chloride. 

Lead — the nitrate and acetate. 

Zinc — the sulphate. 

Aluminium— the sulphate, potash alum, and acetate. 

Tin — the chloride. 

Antimony- — the chloride. 

Calcium — the nitrate, acetate, and phosphate. 

Sodium — the phosphate. 

Barium chloride is the typical lake-forming body for 

sulphonic acids, forming the barium sulphonates which, 

in the greater number of cases, are insoluble in water. It 

is usually sold in the form of crystals, which are colour- 

less rhombic prisms containing two molecules of water of 

crystallization, having the formula BaCl 2 2H 2 0, molecular 

[35) 



36 THE MANUFACTURE OF LAKE PIGMENTS. 

weight 243 - 4(). The crystals are soluble in approximately 
twice their weight of boiling water. They lose their 
water of crystallization if heated to 113° C, fuse at a red 
heat, and, when fused in the presence of air, lose chlorine 
with the formation of baryta : consequently the fused var- 
ieties have often an alkaline reaction. 

Barium chloride is made by dissolving witherite, natural 
carbonate of barium, in hydrochloric acid, or, by fusing 
barytes with carbon, limestone, and calcium chloride, lixi- 
viating the resulting mass with water to dissolve out the 
chloride, and crystallizing the solution so obtained. 

A good sample should, in mass, appear almost part 
white, and a single crystal should appear clear and trans- 
parent. On no account should it contain any iron salts, 
which will give a brownish hue to the bulk, and are easily 
detected by the bluish coloration obtained by the addition 
of a little ferrocyanide solution to a solution of the chloride. 
It should not feel damp to the touch, but quite dry. Free 
acid should not be present, or it will play havoc with the 
colours in course of manufacture. Barium chloride must 
be carefully handled, since, taken internally, it is a very 
violent poison ; and its solutions coming in contact with 
sores cause them often to ulcerate slightly, and their heal- 
ing to be protracted. 

Caustic baryta, Ba(OH) 2 , is used occasionally in the 
production of lakes, in order to procure the entire pre- 
cipitation of colours containing hydroxy groups, which, 
owing to their weak acid property, are unable to decompose 
barium chloride. It is soluble in water to the extent of 
3*5 parts in 100 parts of cold and 90"2 of hot. Caustic 
baryta rapidly absorbs carbon dioxide, and has a strong 
alkaline reaction. As indicated, it is only used in special 
cases, and is not as a rule found in the lake-maker's store. 



LAKE-FORMING BODIES EOR ACID COLOURS. 37 

Nitrate of lead, Pb(N0 3 ) 2 2H 2 0, molecular weight 3661, 
crystallizes in regular octohedrons and is fairly soluble, 
dissolving in approximately its own weight of water. 

Acetate of lead, Pb(CH 3 COO) 2 . 3H 2 0, molecular weight 
378, is extremely soluble, dissolving in eight times its 
own weight of cold water, and in its water of crystallization 
at 755° C. It crystallizes in oblique rhombic prisms, and 
on exposure effloresces. From its sweet astringent taste 
it has obtained the name of sugar of lead which comes into 
the market in two brands — brown and white. For lake 
manufacture the brown variety may be used, — it is a little 
cheaper than the white, — but its use is not to be recom- 
mended for high-class colours. White sugar of lead of 
good quality should be perfectly white in appearance, and 
the crystals should be of fairly large size. There are 
some qualities very white in appearance, and finely crystal- 
line : these do not work well, giving rise to excessive 
frothing, and, where the colours are used in size, causing 
often very considerable annoyance by being responsible 
for the lake rising and running over the machine. As 
with barium chloride, the salt should be perfectly dry to 
the touch. 

The dibasic and tribasic acetates of lead, made by heat- 
ing litharge with normal lead acetate, are of great use in 
dealing with some hydroxy compounds. 

It is, however, much cheaper for the lake manufac- 
turer to make his own nitrate and acetate of lead. They 
can be made from either white lead or litharge. White 
lead can readily be obtained in the form of a pulp con- 
taining 15 to 20 per cent, of water. It works out slightly 
dearer than litharge, but dissolves more readily and with 
less labour than the latter in nitric acid, and when used in 
slight excess ensures the absence of free acid. Lead nitrate 



THE MANUFACTUBE OF LAKE PIGMENTS. 

so prepared can be kept in a solution of known strength, 
thus saving the time and expense incurred in dissolving 
the crystallized salt. 

The normal and basic acetates are most conveniently 
prepared from litharge and acetic acid. Ground litharge is 
not suitable since the action between the fine oxide and 
acid proceeds very rapidly with the evolution of heat, 
causing the ground litharge to set into hard lumps of a 
mixture of litharge and insoluble basic acetate. The best 
method of procedure is to run into an approximately 10 
per cent, solution of acetic acid, at 30° C, the calculated 
amount of litharge required to produce the normal salt, 
roughly 2 cwt. of litharge to 120 lb. of pure acetic acid, 
stirring vigorously throughout the addition. If the litharge 
be added too rapidly, the basic salt separates out with the 
litharge and solution is not readily completed ; in addition, 
excessive rise in temperature results in loss of acetic acid 
by evaporation. When properly made and the proportions 
given carefully adhered to, a solution of the normal acetate 
free from basic acetate is obtained. 

The basic salts are obtained by the addition of the cal- 
culated amount of litharge slowly and with continual stir- 
ring, the normal acetate taking up the lead oxide fairly 
rapidly at first and then more slowly as it approaches 
saturation as tribasic acetate. 

Lead salts possess the power of precipitating a large 
number of dyestuffs, both sulphonic acids and triphenyl- 
methane colours ; but, save for eosines and allied colours, 
their use is not to be advised, since, apart from being far 
more expensive than barium salts, the pigments given are, 
as a rule, much duller than those produced by other pre- 
cipitating agents. In cases where they are suitable, how- 
ever, they demonstrate their suitability in no doubtful way. 



LAKE-FOBMING BODIES FOB A.CID COLOUBS. 30 

In some cases the precipitation is much more complete with 
acetate of lead than with barium chloride, due mainly, in 
all probability, to acetic acid being a much weaker acid 
than the hydrochloric of the barium salt. In any case, 
where there is simultaneous precipitation of an insoluble 
sulphate, the use of lead salts, which are from three to 
four times more expensive than barium chloride, would 
cause such an increase. in the cost of production that 
their use is prohibited. Lead sulphate is much more 
soluble in water than barium sulphate, and very readily 
soluble in solutions of certain salts, especially acetates, and 
this fact must always be borne in mind when dealing with 
this compound of lead in lake manufacture. Yet, as will be 
seen, since the brightest of the lakes obtained from azo- 
sulphonic acid colours are produced by such methods, it 
is perhaps better to retain the use of lead salts simply in 
those few colours for which it is undoubtedly the best 
pigment-forming agent, and which, as a general rule, are 
thrown down on inert bases. 

The two salts of lead which are used for this purpose 
are the acetate and nitrate. The nitrate is considerably 
cheaper than the acetate, and can in many cases be sub- 
stituted for the latter; but, where the question of the 
difference in price between the two can be neglected, the 
use of the acetate is to be preferred, because, should free 
nitric acid be liberated during the reaction, its powerful 
action on the colouring-matter causes great differences in 
shade. 

Of the compounds of antimony the most familiar is 
potassium antimonyl tartrate, better known as tartar 
emetic, 2C 4 H 4 0,;(SbO)K + H 2 0. It forms rhombic prisms, 
soluble at the ordinary temperature in about 15 parts, and 
at the boil in about 3 parts of water. When heated to 



40 THE MANUFACTUBB OF LAKE PIGMENTS. 

200 to 220* C, it loses water, and forms C 4 H 2 6 SbK. 
which on solution reforms tartar emetic. Whether this 
compound can be regarded as a simple tartrate or not 
is doubtful ; evidence tends to show that it should be 
regarded as the potassium salt of a peculiar acid, having 
the following constitution : — 

GACOHj/gOOXsbOH 

Tartar emetic is largely used, both in dyeing and lake- 
making, for fixing lakes produced from basic colours by 
means of tannic acid. In the preparation of lakes, it is 
usually added before the tannic acid. In many cases it 
will be noticed that a slight precipitation takes place, which 
is. in all probability, caused by the combination of the basic 
groups in the colouring-matter with the hydroxy groups 
of the tartaric acid. The lakes produced by its means 
with tannic acid are by far the most permanent ; and 
when tannic acid is used no fixing agent other than tartar 
emetic should be employed, for, of all tannic acid lakes, 
they are the brightest and fastest. 

The oxide of antimony, Sb 2 3 , is used in the same way 
as white arsenic in the precipitation of basic colours, by 
dissolving it in sodium caibonate, and precipitating the 
lake and the base together by the addition of the solution 
to a solution of aluminium sulphate and the colour. It is, 
however, but little used for this purpose. 

Zinc sulphate, ZnS0 4 7H 2 0, white vitriol, is used in 
some cases to precipitate eosines, but its application is 
limited. It is a white crystalline solid, fairly soluble in 
water, and is decomposed by the action of normal sodium 
carbonate into basic carbonates, and zinc hydrate. In 
some instances, notably in that of the Marine Blue of 



LAKE-FORMING BODIES FOB A.CID COLOURS. \\ 

ML, B, and the Erioglaucines, a small percentage of 
the mixed carbonate and hydrate so produced, mixed with 
the base, leads to much more complete precipitation of the 
colouring-matters than would otherwise be obtained. 

Aluminium salts. — The salts of this metal, notably the 
sulphate and the acetate, are by far the most important 
reagents at the command of the lake-manufacturer. Their 
value does not lie in their ready precipitation of the colour- 
ing-matters, since, with very few exceptions, the addition 
of an aluminium salt to the solution of a colouring-matter 
produces no apparent change, but in the fact that they 
form a source of aluminium hydrate, AL(OH) (i . The latter 
can act either as an acid or basic substance according to 
conditions, and in consequence of this property is able to 
play the part of a powerful auxiliary in the precipitation 
of colouring-matters, and to combine with other bodies 
giving insoluble aluminium compounds, which are an im- 
portant class of lake bases. 

Aluminium sulphate, Al 3 (S0 4 ) 3 H a O.— This salt is ex- 
tremely soluble in water and comes into the market in 
various forms, very rarely crystalline. It is usually 
sold as guaranteed to contain a certain percentage of 
ALO a . Lump aluminium sulphate usually contains from 
11 to 16 per cent, of Al 2 O s ; but this quality is apt to 
contain a considerable quantity of iron. The best make 
is a fine dry white powder, containing about 17 per cent, 
of Alg0 3 ; this, and this alone, should be used in the manu- 
facture of pigments, since it is much purer and more 
reliable than other qualities having very little difference in 
price to recommend them. 

The best guides to the selection of a sulphate of alu- 
minium are — the colour, which should be quite white ; the 
percentage ALO : , content ; and freedom from iron. The 



42 THE MANUFACTUKE OF LAKE PIGMENTS. 

presence of 05 per cent. Fe^O^ is sufficient to render a 
brand utterly unsuitable for the production of alizarine 
lakes. 

The salt has a strong acid reaction, and is decomposed 
by the action of sodium carbonate, thus — 

A1 2 (S0 4 ) 3 + Na 2 C0 3 + H,0 = Al 2 (SOJ 2 (OH) 2 + Na 2 S0 4 + CO, 
Al 2 (S0 4 ) 2 (OH), + Na 2 C0 3 + H 2 = Al 2 S0 4 (OH) 4 + Na 2 S0 4 + C0 2 
Al 2 S0 4 (OH) 4 + Na 2 C0 3 + H 2 = Al 2 (OH) 6 + Na 2 S0 4 + C0 2 

If the solutions of sulphate and carbonate be very 
dilute and cold, no permanent precipitation takes place 
until a considerable quantity of sodium carbonate has been 
added, since the basic sulphates formed do not separate 
at low temperatures. This property can be taken advan- 
tage of in producing pale aluminium lakes, by adding the 
colour, for example, methyl-violet B, to a solution of basic 
aluminium sulphate, and inducing complete precipitation 
of the aluminium hydrate by adding slowly the requisite 
amount of soda and raising the temperature. The basic 
sulphates of aluminium have a very considerable attraction 
for basic colouring-matters. 

When the solutions of sodium carbonate and aluminium 
sulphate are hot and concentrated, the precipitate is gener- 
ally very lumpy, and, if there be an excess of aluminium 
sulphate present, combination between the hydrate already 
formed and the excess takes place, giving the precipitate 
a semi-crystalline appearance. 

The acetate of aluminium is in its chemical behaviour 
very similar to the sulphate, save that the basic salts are 
more stable than those of the latter. It is prepared, either 
by dissolving the hydrate in acetic acid, or by heating a 
solution of aluminium sulphate with sugar of lead. 

It is of far greater importance in dyeing and calico 



LAXE-FOBMING BODIES FOB ACID COLOTJBS. 43 

printing than in lake-making. In the latter industry it 
is only substituted for aluminium sulphate in those cases 
where the presence of sulphuric acid is objectionable. 

Hydrate of aluminium, Al.,(OH) (i .— This body is pro- 
duced when caustic soda or potash, ammonium hydrate or 
an alkaline carbonate is added to a solution of an aluminium 
salt ; it is soluble in caustic alkalies, and is therefore usually 
precipitated by means of the carbonates. 

When produced from cold dilute solutions, aluminium 
hydrate is of a transparent gelatinous nature, but, on heat- 
ing, becomes opaque, and more contracted in bulk. If 
precipitated from hot solutions with ammonia, it is thrown 
down in the form of a light opaque precipitate. With car- 
bonated alkalies the precipitate is much more dense, and 
is very lumpy, owing to the reaction being incomplete. 

The form in which aluminium hydrate is brought into 
contact with colouring-matters determines largely the 
amount of colour with which it combines. Whether with 
hydroxy compounds the aluminium lake is more readily 
formed, or there is merely mechanical absorption, is a moot 
point ; but the fact remains that the addition of a colour 
to aluminium hydrate produced in the cold, and subse- 
quent boiling, fixes more colour than when the lake is 
produced hot from the same materials, or when the pro- 
duction of the aluminium hydrate itself takes place, in 
presence of the colour, in hot concentrated solutions. 

When the colours are intended for dry pigments it is 
advisable to precipitate the aluminium hydrate from fairly 
concentrated solutions ; otherwise the lakes dry very hard, 
instead of being friable. 

Aluminium hydrate, when dried, forms a hard white 
horny substance, which has the composition AL(OH) s , 
and only on ignition is the whole of the water driven off, 



44 THE MANUFACTUBE OF LAKE PIGMENTS. 

leaving AL0 3 . The conditions under which it is produced 
influence the nature of the dried substance, and a careful 
study of this point is very essential when producing lakes 
in which aluminium hydrate forms the greater part of the 
base. This is dealt with more fully in Chapter VI., under 
lake bases. 

It occurs naturally as bauxite, and, when finely ground, 
forms a valuable filler in conjunction with the more dense 
minerals used for this purpose. 

Of the tin salts, stannous chloride, SnCl 2 2H 2 0, which 
crystallizes in transparent monoclinic prisms, is the only 
compound used. It dissolves in its water of crystallization 
at 40° C, is hygroscopic, and is only stable in concentrated 
solutions, decomposing on dilution, forming a basic chloride 
which is insoluble in water. This salt is but little used 
since its powerful reducing action destroys the shade of 
many of the artificial colours. It forms the basis, how- 
ever, for the preparation of those stannic acid compounds 
used in the manufacture of special lakes from basic colours, 
especially greens and blues. 

Calcium salts are not used as precipitating agents, but 
the acetate and nitrate are employed to introduce into cer- 
tain lakes, e.g., the alizarine compounds, the calcium which 
is an essential factor in their composition : they can, in 
fact, be more properly regarded as assistants to the lake- 
forming bodies proper. 

The necessity of employing calcium salts absolutely free 
from iron, in the manufacture of alizarine lakes, is very 
important. The author has found the following method 
of purification efficient. Dissolve the chalk, or any calcium 
salt, in hydrochloric acid ; add a little chlorate of potash to 
oxidize any iron present, and then excess of disodium hy- 
drogen phosphate, precipitating the mixture with excess 



LAKE-FOBMING BODIES FOB ACID COLOUBS. 45 

of ammonia. Wash the precipitate well by decantation 
with distilled water, and treat with acetic acid. This 
readily dissolves the calcium phosphate, leaving the iron 
and aluminium as insoluble phosphates. Filter and decant 
the clear solution which will be found quite free from any 
contamination with iron. 

Sodium acetate, CH 3 COONa3H 2 0, is also largely used 
in lake manufacture. It is introduced into various mix- 
tures for two reasons : firstly, because in presence of a free 
miueral acid it is decomposed with the liberation of acetic 
acid, which has but little action, in comparison with the 
stronger acids, on the various ingredients of a lake pig- 
ment ; and secondly, its faint alkalinity in many cases 
enables the shade and brilliancy of the colour to be fully 
developed, this object not being attainable in the presence 
of free strong acid or alkali. 

Sodium acetate crystallizes in monoclinic prisms, and 
is soluble in about half its weight of boiling water. A 
tartar emetic and tannic acid lake made in the presence of 
this salt settles readily : in its absence there is sometimes 
considerable difficulty in washing the lake thoroughly, 
since the pigment either remains in suspension or settles. 
only very slowly. 



CHAPTEE V. 

LAKE-FORMING BODIES FOR BASIC COLOURS. 

Just as the acid colours behave as simple acids, so the 
basic colours act as simple bases, and it will be found 
that the lakes formed from basic colours are combinations 
of the latter with some acid or semi-acid body. The acids 
most commonly used for this purpose are tannic, phos- 
phoric, arsenious, antimonious, stannic, resinic, and palm- 
itic, stearic, and allied fatty acids. 

The most important of these, in respect of producing 
the fastest and most satisfactory lakes, is — 

Tannic acid, digallic acid.— Tannin, C (i H,(OH) a COOC, ; 
H;,(OH)oCOOH, is a weak astringent acid substance de- 
rived from gall nuts, formed by the action of insects on 
certain trees and shrubs, and from sumach, the twigs and 
leaves of an Italian shrub, by extraction with water and 
alcohol. Its constitution may be expressed by the following 
formula : — 

HO x .OH 

HCK x CO x 

HCX /O / 

>C 6 H 2 < 

HCK x COOH 

Tannic acid is sold in various brands, containing more 

or less free acid. A good variety only should be used for 

the formation of pigments, and this should be of a pale 

yellowish-brown colour. It should be kept in closed 

(46) 



DAKE-FORMING BODIES FOB BASIC COLOURS. 4 1 

vessels, since under the action of air and light it undergoes 
considerable change. 

In alkaline solutions tannic acid absorbs oxygen, darken- 
in» in colour. Its aqueous solutions are precipitated by 
dilute mineral acids, except nitric acid, and by sodium and 
potassium chloride and potassium acetate, but not by 
( rlauber's salts. 

It is a monobasic acid, decomposing carbonates, and 
forming, with various metallic oxides, insoluble salts. 

Tannic acid is fairly expensive, and is used only for the 
purest shades of colour. It is customary for deep shades, 
in which the yellow or brownish tint imparted by the colour- 
ing-matter in the acid is not harmful, to use extracts of 
sumach derived from the twigs of several plants of the 
genus BJms, the finest variety of which comes from Sicily, 
and of myrobalans the fruit of Termanalia Chebula, a tree 
common in India. For dark blues and greens, galls or 
extract of galls can be used with advantage. 

Phosphoric acid, H :j P0 4 . — Of the various acids of phos- 
phorus only normal phosphoric acid is usually employed in 
the manufacture of pigments. 

The free acid, however, is not employed as such but 
in the form of a salt known commercially as phosphate 
of soda, which is really disodium hydrogen phosphate, 
Xa.,HP0 4 10HoO. This salt, when added to a solution of 
a basic dye, e.g., Methyl Violet or a Khodamine, does not 
precipitate the colouring-matter, unless the addition results 
in the formation of an insoluble phosphate at the same 
time. The latter is usually obtained from an aluminium 
salt. 

Disodium hydrogen phosphate, though seemingly an 
acid salt, lias a faintly alkaline reaction, and is readily 
soluble in water. When used for the production of the 



48 THE MANUFACTURE OF LAKE PIGMENTS. 

insoluble phosphates of aluminium, calcium, or barium, it 
should be remembered that it is an acid salt, and free acid 
is often liberated during the precipitation. Nearly all the 
phosphates being readily soluble in dilute acids, precipita- 
tion under such conditions is not complete, and the re- 
sultant product is slimy, unfilterable, and unusable. If 
the solutions be rendered alkaline, complete precipitation 
is obtained, but the colour is almost entirely redissolved. 
When using disodium hydrogen phosphate it is advisable 
to add to it almost sufficient soda to neutralize any free 
acid that may be liberated, but the addition should not 
be sufficient to give an alkaline solution. The molecular 
weight of disodium hydrogen phosphate is 322, and it re- 
quires another atom of sodium to change it to the normal 
salt. This is contained in 53 of sodium carbonate, XaoC0 3 , 
and the addition, therefore, of soda ash to the extent of 
one-sixth the weight of disodium hydrogen phosphate used 
will give approximately the conditions required to prevent 
the formation of free acids. In this case the precipitation 
of the pigment takes place in the presence of a large excess 
of the precipitating agent, and therefore the calculation as 
to the quantity of precipitating agent required for the 
colour may be neglected, the only calculation being the 
quantity of colour required to give a given shade with a 
given quantity of base, or rather of materials about to be 
used. 

Arsenious acid, H 3 As0 3 . — The solution of arsenic tri- 
oxide in water yields a solution of this acid, which, how- 
ever, is very unstable, although its salts are extremely 
stable. As with phosphoric acid, the sodium salts are used 
in the preparation of lakes. 

These salts are not usually bought by the lake-manu- 
facturer, but are prepared by him by dissolving white 



LAKE-FORMING BODIES FOB BASIC COLOURS. 4 ( .) 

arsenic or arsenic trioxide in sodium carbonate. Neither 
the normal nor the hydrogen salt effects any precipitation 
when added to a solution of a colouring-matter, say Ethyl- 
green Crystals (Ber), lake formation only taking place when 
an insoluble arsenite is precipitated in the presence of the 
colouring-matter; and it appears that the lake-forming 
properties of both this acid and phosphoric are exercised 
only when combined with some metal forming a compli- 
cated acid salt. Such are produced when solutions of the 
alkali salts of these acids are added to a solution of an 
aluminium salt, and it is to be assumed that these arsenical 
and phosphoric aluminium compounds fix the dye, the reac- 
tion being not one of simple precipitation by a polyhydroxy 
acid. This is confirmed by the fact that the addition of 
a colour to the thoroughly washed precipitate, formed by 
the interaction of a solution of aluminium sulphate, and 
an alkaline arsenite or phosphate, results in its fixation. 

Great care must, however, be taken in the use of both 
these acids, so that at the completion of the reaction the 
supernatant liquor is neutral or very slightly acid ; and, in 
dissolving arsenic trioxide in sodium carbonate, such 
amount of sodium carbonate must be used that, when the 
solution is added to the aluminium salt, these conditions 
are fulfilled. This, of course, entails a careful examination 
of the raw materials used, otherwise variable results will 
be obtained. 

Stannic acid and meta-stannic acid are used for the 
preparation of lakes from basic colours, but owing to the 
feeble attraction of the latter for colours, its application is 
limited. Stannic compounds are used for the production 
of some green lakes which are more brilliant than the 
tannic acid greens, but not equal to those produced by 
arsenious acid, in view of their less poisonous character. 



•50 THE MANUFACTURE OF LAKE PIGMENTS. 

Stannous chloride, which decomposes into the basic 
salt, when added to some colours, precipitates them ; the 
further addition of tannic acid deepens and renders the 
shade duller but faster. 

Stannic chloride, on addition to basic colours in alkaline 
solutions, is decomposed into stannic hydrate, which is 
thrown down together with the tin lake, if the solution be 
not too strongly alkaline. The tin lakes require great 
care in their manipulation, and are rarely met with, al- 
though those prepared from natural colours, such as fustic, 
Persian berries, etc., are of considerable importance. 

The acids of antimony are similar to, and are applied 
in the same way as, those of arsenic. 

Colophony, or rosin, contains resinic acid, which dis- 
solves very readily in sodium carbonate giving a solution 
of what is generally known as rosin soap. It is largely 
used to produce brilliant magenta and green lakes, by 
precipitating the basic colours in conjunction with a 
metallic resinate, such as the lead, zinc, or aluminium 
compound. The rosin lakes are nearly all soluble or ap- 
parently soluble in oils and varnishes, and the metallic 
resinates forming the matrix of the compound being trans- 
parent in oil if properly made, complete the appearance of 
solubility. They are certainly very brilliant, and have 
a considerable demand among wall-paper manufacturers. 
For stencil inks and tin printing the process adopted and 
the precautions to be observed are similar to those in the 
making of phosphoric and arsenical lakes ; but for oil or 
lithographic work the rosin lakes are useless and are about 
the most fugitive lakes produced from basic colours. 

The use of various fatty acids, in the form of soaps, 
except in conjunction with some other precipitating agent, 
is not to be recommended for throwing down basic colours ; 



LAKE-FORMING BODIES FOB BASIC COLOURS. 51 

but considerable use is made of these acids, both in the 
form of soaps, and as soluble preparations of the free 
acids, such as occur in the various sulphated and soluble 
oils, when amido-acid colours are being transformed into 
lake pigments, since their property of combining with the 
basic groups fixes the colour more completely, and gives 
brighter and clearer shades. 

They must, however, be used in small quantities only, 
and with great discrimination and care ; otherwise they 
are apt to make the colour bleed, causing a loss of colour- 
ing-matter and deterioration of the shade. 

Sulphonated castor-oil, neutralized with ammonia, rather 
than soda, is of more importance as an assistant in the 
production of lakes than as an actual precipitant. It 
certainly combines with and precipitates colours, but the 
resultant lakes are unsatisfactory. Slight additions of this 
material to the lake, after the usual procedure has been 
carried through, not only, in many cases, completes the 
precipitation, but also modifies the precipitate in such a 
way as to facilitate its filtration and preparation for use, 
besides modifying it in other important particulars which 
are more fully dealt with in the next chapter. 



CHAPTER VI. 

LAKE BASES. 

Hitheeto the production of the lake proper has been 
dealt with, but in order to develop the full value of the 
colour, attain the maximum brilliancy of colour, and to 
impart to the pigment such physical properties as opacity, 
friability, covering power, and density, which are rarely if 
ever characteristics of the pure lake, it is essential that the 
colouring-matter should be thrown down on or together 
with some suitable medium. 

The manufacture of lake pigments may be likened to 
dyeing, for the dyer has to produce a given shade on cloth 
or yarn, while the lake-maker has to produce a given shade 
on some base or bases, and his lot is the harder, inasmuch 
as the bases, as a general rule, have no affinity for the 
colouring-matter of which he can take advantage. In 
many cases, also, it is essential that the base possess cer- 
tain definite properties, if the finished lake is to be suitable 
for the purpose for which it is designed ; and, in matching 
a pigment, not only has the shade and strength to be 
correct, but the base must also be matched, if the pro- 
duct is to be satisfactory in every way. Though the lake- 
maker escapes the complications of the dyes arising from 
the variation of similar fibres from different sources, the 
chemical and physical nature of the base or matrix on 
which the lakes are developed, whether it be a simple 

inert body or a complex mixture obtained by precipitation, 

(52) 



LAKE BASES. 53 

needs as much if not more consideration and study than 
the actual production of the lake itself. Considerable 
experience in the production of lake pigments on a com- 
mercial scale renders it a moot point whether the conver- 
sion of the colouring-matter into an insoluble pigment, or 
the adjustment of the bases to suit the requirements of 
the various uses of the pigments, is the key to their suc- 
cessful and economical manufacture. 

It would be advisable, perhaps, at this stage to consider 
the exact function of the base in a lake pigment. We 
have seen in Chapter I. that a lake is usually understood 
to be a dyestuff converted into an insoluble coloured com- 
pound ; but, in the majority of cases, this compound does 
not become a workable pigment, until it is combined with 
some other body or bodies giving to it those physical 
properties without which its practical application would 
be impossible. 

There is a considerable difference between the base of 
a lake, and the filler or extender that is used in the paint 
trade to let down strong colours. A lake containing 10 
per cent, of eosine on barytes is definitely understood to 
mean a pigment containing 10 per cent, of eosine lake 
struck on 90 per cent, barytes ; but a 20 per cent, eosine 
lake on barytes, let down with barytes until it contained 
10 per cent, of colouring-matter, cannot properly be called 
a 10 per cent, eosine lake pigment, though if the mixture 
were well made there would be very little difference between 
the two products. The struck 10 per cent, eosine lake 
pigment would be the better article, since the lake would 
be more evenly and intimately spread over the whole of 
the barytes, but, in preparation, there would be greater 
bulk to handle and dry, with consequent increased 
labour and expense. It behoves the manufacturer of lake 



54 THE MANUFACTURE OF LAKE PIGMENTS. 

pigments to determine, when considering cases, of which 
this is but a very simple example, the most economical 
quantity of base it is desirable to use. This question 
becomes a very serious one in the production of such pig- 
ments as those produced from Lithol Red R and other 
pigment colours, and will be more fully discussed when 
dealing with the production of pigments from this class 
of colouring-matters. 

There are some lakes, of which the alizarine lakes are 
typical, which may be looked upon as lakes pure and 
simple, capable of being used without the addition of 
anything that may be called a base. For the develop- 
ment of the colouring-matter, the latter must be treated 
with aluminium, calcium, stearine, and certain other colour- 
less bodies which, by direct combination with the alizarine, 
give rise to a coloured compound, known as the lake. The 
shade and intensity of the lake produced depends not only 
on the nature of the colouring-matter, but on its state 
of combination in the finished product. The shade and 
strength of these lakes, however, may be varied by the 
amount of colouring-matter used, and, therefore, the com- 
plex mixture of acid salts which are capable of developing 
the colour of alizarines must be looked upon as the base 
in these pigments. 

Basic colours, which are absorbed by white and green 
earth, and form fairly stable combinations, e.g., malachite 
green, can be regarded in somewhat the same way. The 
earths referred to consist mainly of siliceous matter natur- 
ally impregnated with compounds of organic origin which 
combine with the dyestuffs, the shade and strength of the 
pigment produced being determined by the amount of 
colour that is absorbed or enters into combination. The 
green earth is also a determining factor in the nature of 



LAKE BA8ES. 55 

the resulting product in so far as it has not an unlimited 
capacity for absorbing colouring-matters, this property 
heing governed by its quality, which again depends on its 
source and mode of preparation for use. 

It is perhaps therefore advisable to divide the bases 
used for lake pigments into three divisions: — 

(a) Those in which the base acts merely as an ex- 

tender and has no chemical relationship with 
the colour lake. 

(b) Those in which the base and the lake are in de- 

finite chemical combination. 

(c) Those having the combined properties of (a) and [b). 
There can be defined, however, no sharp line of 

demarcation where a base ceases to be a base and becomes 
a filler or extender. Especially is this true in the case of 
pigment colours on barytes or other similar base, where 
anything from '2 per cent, to oO per cent, of colouring- 
matter may be required ; but terra-alba and china clay 
present in an alizarine lake and green earth colour respec- 
tively, could not be regarded as anything but diluents. 

The following is a list of the substances usually com- 
posing the majority of bases. Most are insoluble in water, 
and are either used in the form mentioned, or are produced 
at the same time as the lake, or during some operation in 
the production of the pigment : — 

I. Barium sulphate, as barytes (natural) and blanc-fixe 

(precipitated), BaS0 4 . 
II. Clay. — China clay, a compound silicate of aluminium. 
III. Calcium sulphate. — Paris white, gypsum (natural). 

satin white (precipitated), CaS0 4 . 
I V. Kieselguhr. 
V. Red lead. 
VI. Zinc oxide. 



56 THE MANUFACTURE OP LAKE PIGMENTS. 

VII. Lead sulphate, PbS0 4 . 
VIII. Aluminium hydrate, Al 2 (OH) 6 . 

IX. Phosphate of aluminium, A1P0 4 . 

X. Aluminium arsenite. 

XL Phosphate of barium, Ba 3 (P0 4 ) : ,. 
XII. Phosphate of calcium, Ca 3 (P0 4 ).,. 

XIII. Lamp and vegetable black (carbon). 

XIV. Green and white earth. 
XV. Lead carbonate, white lead. 

XVI. Calcium carbonate, chalk. 
XVII. Lithophone. 
XVIII. Orange lead. 

These compounds are introduced into the pigment by 
grinding, as in the case of the pigment colours, by suspen- 
sion in the solution from which the lake is precipitated, by 
formation from suitable reagents at the time of precipita- 
tion of the lake, or by a combination of the two latter 
methods, e.g., when using mixed bases, suspending one in 
water and producing the other simultaneously with the lake. 

Barium sulphate occurs naturally as heavy spar, and, 
when ground, comes into the market under the name of 
barvtes. According to the traces of metals it contains, it 
is coloured grey or brown ; but for all classes of pigment- 
making only the pure white, very finely ground product 
should be used. It possesses but little covering power in 
oil, and, when used for the preparation of pigments for 
oil-work, it is advisable to mix with it lead sulphate in 
the case of cheap goods, or lead carbonate and red lead 
(when shade allows) for those of better quality. For sonic 
classes of pulp colours, barytes is extremely valuable, since, 
compared with other bases, it gives very bright and full 
shades with small amounts of colouring-matter. 

The precipitated variety is obtained by precipitating 



LAKE BASES. 57 

the sulphate from a soluble barium salt, by means of 
sulphuric acid. The fineness of the particles, on which 
the quality greatly depends, is varied according to the 
method of precipitation. This product is now available 
in the market in fairly large quantities both in pulp and 
dry. but, where uniformity of quality is desired, it is 
always advisable for the lake manufacturer to prepare it 
himself. To secure uniformity, the essential requirements 
are : both the solution of the soluble barium salts and that 
of the sulphate, whether it be sulphuric acid or a soluble 
sulphate, must be always of the same concentration ; the 
stirring of the mixture, the method of addition, and, above 
all, the temperature at which the blanc-fixe is struck must 
not vary. Sulphuric acid may be used, but it is preferable 
to use a soluble sulphate : Glauber's salt or sodium sul- 
phate is the one generally selected, because it is cheap. 
The sulphate should be added just slightly in excess, in 
order that the whole of the barium may be thrown down. 
Witherite, native barium carbonate, can be used as the 
source of the barium salt. Dissolved in hydrochloric acid, 
in the presence of an excess of the mineral, a solution of 
barium chloride is obtained fairly free from iron, since the 
witherite, when in excess, causes the reprecipitation of any 
dissolved iron compounds. 

The precipitated barium sulphate settles very readily, 
and must be washed free from acid, if acid has been 
used in its production. In many cases the product is too 
fine to filter-press economically, but this difficulty is readily 
overcome by the addition of a little ammonia neutralized 
sulphonated castor oil, about O'l per cent, of the weight of 
BaS0 4 to be separated ; this causes the particles of the 
blanc-fixe to become flocculent, allowing the whole to be 
readily filter-pressed, and in no way injuring the properties 



58 Till; MANUPACTUEB OF LAKE PIGMENTS. 

or nature of the material to which it has been added. 
Precipitated barium sulphate is known commercially as 
blanc-fixe, permanent white, and enamel white, and is 
largely used as a base for pulp colours, since it gives a 
fine solid appearance, and, above all, works out on paper 
perfectly smoothly, differing in this respect from barytes, 
which, however finely ground, imparts a rough feeling to 
any pigment that it contains, rendering it an unsuitable 
base for pulp colours for surface papers. There is a great 
difference in the shade produced when equal weights of 
colour are precipitated in the same way on equal weights 
of barytes and blanc-fixe, the shade on barytes being much 
fuller and brighter than that on blanc-fixe, which is, in 
addition, frequently of a different tone. 

Pulp colours made purely from either of these varieties 
of barium sulphate retain but little water, and soon be- 
come hard and dry. 

China clay, or kaolin, a naturally occurring substance, 
is a hydrated silicate of aluminium, derived from the clay 
of felspathic rocks, and, when of good quality, contains 
only traces of impurities, in the form of oxides of iron, 
calcium, and magnesium. It forms an extremely valuable 
base for lakes, especially in combination with other bodies ; 
and is capable of retaining about 60 per cent, of water, giv- 
ing pulps of a smooth appearance and finish. Like barium 
sulphate, it has no chemical affinity for dyes, though it is 
often coloured by being saturated with solutions of colour- 
ing-matters, which, however, can be entirely removed by 
washing. Lakes in which a large proportion of clay has 
been used are apt to have a "chalky" and "bright" 
appearance, which detracts very considerably from their 
value, and rather dulls the shade ; also in the final wash- 
ings the clay has a tendency to hang, taking a very con- 



LAKE BASES. 59 

siderable time to settle. In combination with hydrate of 
aluminium these objectionable qualities largely disappear. 
Such combinations can be more readily discussed when 
dealing with other similar aluminium hydrate mixtures. 

China clay, whose density is much less than that of 
either gypsum or barytes, is used mixed with these bodies, 
to give lightness and to diminish their coarseness. With 
some lakes, more especially the pulp lead eosine lakes, the 
use of china clay in conjunction with blanc-fixe makes the 
pulp less tenacious, and lighter, and, by causing the lake 
to retain more moisture, improves the keeping qualities 
and yield. 

Calcium sulphate, gypsum, Paris white, occurs naturally 
as satin spar, gypsum, alabaster, etc. The whole of the 
water of the naturally occurring body CaS0 4 + 2H 2 is 
driven off between 110° to 120° C, the residue being known 
as burnt gypsum or plaster of Paris, which can be readily 
identified by its property of combining with water, with 
evolution of heat and subsequent solidification. When 
heated above 200° C. gypsum becomes "dead burnt," and 
then only takes up water slowly, without hardening. 

Calcium sulphate is distinctly soluble in water, much 
more so in the presence of ammoniacal salts — especially of 
acetates. It is readily soluble in strong hydrochloric acid, 
and this solubility sometimes causes it to be overlooked in 
the cursory examination of lakes. 

Owing to its solubility, it is not a suitable agent for 
use in the preparation of lakes by precipitation. 

A mixture of calcium sulphate and aluminium hydrate, 
known as satin white, made by adding potash alum to milk 
of lime and stirring the mixture until the reaction is com- 
plete, is largely used in the surface and wall paper trade 
for producing fine smooth finishes. It is alkaline in its 



60 THE MANUFACTURE OF LAKE PIGMENTS. 

reaction, and care must be taken with colours, especially 
reds, used in conjunction with this material, that they are so 
prepared as to prevent bleeding when mixed with it in size. 

Terra-alba is largely used in the manufacture and reduc- 
tion of dry pigment colours, since it is much lighter, and 
of greater covering power, than barytes. 

Ked lead, or minium, Pb d 4 , litharge, PbO, and orange 
lead, red lead free from litharge, are chiefly used, in pro- 
ducing shades of vermilionettes and permanent reds, in 
conjunction with other bases, such as barytes, lead sul- 
phate, and lead carbonate, and other lakes which are used 
as paints, in order to modify the shade and improve the 
body and covering power. 

Orange lead is the only oxide of lead which should be 
used in the preparation of lakes ; the other oxides act very 
powerfully on linseed oil, and, when used to reduce the 
price of the pigment, render it of no value whatever for 
use with oil as a paint. 

Lead sulphate, PbS0 4 , is used mainly as a base instead 
of barytes, for intermediate classes of colours. For paints 
where the price prohibits the use of white lead, or where 
the reactions involved in the formation of the lake would 
decompose the carbonate, a cheap useful sulphate of lead, 
known as " lead bottoms," can be obtained. This is a bye- 
product obtainable from calico print-works and paper- 
works, and being a precipitated sulphate is very fine, and 
gives excellent results. It contains some impurities, and 
requires thorough washing before use as a lake base. 

White lead, or lead carbonate, is used only for paint 
colours ; its well-known physical and chemical properties 
do not call for treatment here. 

Zinc white, ZnO, is rarely used alone as a lake base, 
though, like the lead compounds, it finds application 



LAKE BASES. 61 

occasionally in the manufacture of oil colours. It is, how- 
ever, of great use in the production of azure blues from the 
Erioglaucines and Patent Blues of L, M, and B. since for 
some reason, when present in small quantities in the base 
used, the colour is more completely thrown down. The 
explanation of this cannot be satisfactorily given, but 
nevertheless the presence of from 2 to 6 per cent, saves 
considerable colour. 

Lithophone, a mixture of precipitated barium sulphate 
and zinc sulphide, containing in good qualities about 30 
per cent, of zinc sulphide, is not used in the precipitation 
process, as the slightest acidity would lead to the decom- 
position of the zinc sulphide ; but, in dry grinding of such 
pigments as Helio Fast Red R. L., where greater body and 
covering power are needed than blanc-fixe gives, it is used 
to a fairly considerable extent. 

Lamp, vegetable, and allied blacks are used as bases for 
deep shades of olive-green and blue, being first made into 
a paste or thin cream with water — easily effected if the 
operation is started with a little glue and ammonia, and 
water added until the proper consistency is obtained — 
and then the required colours added and precipitated with 
or without the addition of any other base. 

Chalk, or calcium carbonate, CaC0 3 , which occurs native 
as limestone, chalkstone, marble, etc., and in its artificial 
form as precipitated chalk, is but little used in the manufac- 
ture of pigments, owing to its sensitiveness to the action of 
the weakest acids ; but it is of great service when employed 
in small quantities to eliminate traces of acid. If used in 
large quantities, owing to its solubility in water contain- 
ing carbon dioxide, it gives a milky appearance to the pulp 
colours when worked with size, and the other bases give 
more pleasing effects without many of the drawbacks that 



62 THE MANUFACTURE OF LAKE PIGMENTS. 

this body has, such as frothing when worked with size. 
For paint colours these objections do not so much apply 
as for pulp, but chalk is not a base to be recommended. 

Kieselguhr, a finely divided infusorial siliceous earth, 
largely used in the manufacture of dynamite, is used with 
the heavier bases to make the lake lighter. It finds its 
widest application in pulp colours where such bases as 
barytes and blanc-fixe are used, since the latter retain but 
little moisture, while kieselguhr possesses the property of 
retaining a large amount of water without becoming too 
thin and pulpy, rendering the pigment more easily worked 
in size, etc., besides increasing the body and density -of-the 
colour. 

Green earth. — This is a similar substance to kieselguhr, 
and has the property of taking up, and being dyed by, basic 
colours, notably greens and blues, giving highly coloured 
bodies of much superior fastness in every respect to the 
lakes produced by the ordinary methods. They are fast to 
weak alkalies and have a great vogue in distemper work. 
Analysis of the earth shows it to be a mixture of hydrat'ed 
oxide of iron, silica, and calcium compounds, together with 
a variable amount of nitrogenous organic matter of an 
acid nature. Varieties of green and white earth differ very 
considerably in their capacity for taking up colours and 
forming satisfactory lakes, this variation being dependent 
on the manner in which they are prepared for market and 
the nature and amount of organic matter they contain. 

Apart from its colour white earth is very similar to 
green earth and possesses the same properties, but does 
not give quite such satisfactory, though brighter, results. 

The presence of hydrated oxide of iron in these two 
earths may in some measure account for the properties of 
the earth, for in the presence of the organic matter it 
may have all the action of a strong iron mordant. 





Manufacture op Lake Pigments 



To face page 62 



LAKE BASES. 63 

On Plate II are shown a scries of shades given by basic 
dyestuffs on Green Earth : — 

No. 1 shows 2 7 Auramine (Brit. Dyes) on Green Earth. 

No. 2 .. „ Chrysoidine YEP 



No. 3 
No. 4 
No. 5 
No. 6 



Bismarck Brown 

Methylene Blue 2 B 
Methyl Violet 
Magenta Crystals 



In Plate Ila (Frontispiece) are shown a series of shades 
given by basic dyestuffs on White Earth : — 

No. 1 shows 1 Auramine O (Brit. Dyes) on White Earth. 

No. 2 „ „ Chrysoidine YEP 

^ o |0 - 6 °/ Malachite Green Crys. ,, 

" (04 7 Auramine O 
No. 4 „ 2 7 Methylene Blue 2 B .. 
No. 5 „ 1 7 C Methyl Violet 
No. 6 ,, ,, Magenta Crystals 

Aluminium hydrate, AL(OH) (i , is rarely used other than 
freshly prepared, and the preparation is usually effected by 
precipitation from the solution of a soluble salt, usually 
sulphate of aluminium, with sodium hydrate or carbonate, 
the carbonate being generally employed. The reaction 
which takes place can be expressed as follows : — 

AUS0 4 ) 3 + Na,C0 3 + H.,0 = Al.,(S0 4 ).,(OH) 2 + Na 2 S0 4 + CO., 
Al.,(S0 4 ).,(OH)., + Xa,CO, + H.,0 = Al,S0 4 (OH) 4 + Na,S0 4 + CO."; 
Al,(S0 4 )(OH)/+ Na;C0 3 + HX> = Al 2 (OH), + Na 2 S0 4 + CO.] 

The formation of the basic sulphates takes place more 
readily in cold dilute solution, and, of them, notice need 
only be taken when dealing with cold dilute precipitations, 
where their formation, in the absence of enough alkali, 
may lead to a loss of weight, owing to their solubility. 
The basic compounds, are, however, decomposed by heat. 

Sodium hydrate is very rarely used to effect this pre- 
cipitation, since aluminium hydrate acts like a weak acid 
with strong bases forming aluminate, and in consequence 
is easily soluble is an excess of this reagent. 



64 THE MANUFACTURE OF LAKE PIGMENTS. 

On the proper preparation of the alumina the produc- 
tion of the best results depends, for, if the solutions used be 
too strong, the alumina is imperfectly precipitated, and the 
finished lake permeated with numerous white specks. If 
an excess of alkali is used, a greater proportion of barium 
chloride has to be employed, with consequent weakening 
of the shade, and the resultant pigment often bleeds. If 
the solutions be too dilute and cold the precipitation is 
frequently only partial, and the lake has a tendency to 
"hang," i.e., not to settle in the subsequent washing 
operations. 

Potash alum, owing to its greater cost and greater 
insolubility in water, is used only in the manufacture 
of those lakes which are required to have a fine frac- 
ture, in order to obviate the danger arising from too 
strong solutions : but aluminium sulphate can be used 
just as well, if care on the points of dilution and tempera- 
ture be observed, for the strength of solution which would 
give good results with an ordinary pigment would, owing to 
the greater flocculency of the particles, be unsatisfactory 
in the case of a lake required to show a clean fracture. 

Pigments containing a large proportion of alumina 
often tend to dry very hard and are difficult to work. This 
difficulty can frequently be overcome, without deteriorating 
the quality of the lake, by the addition of from 5 per cent, 
to 20 per cent, of disodium hydrogen phosphate which is 
precipitated as aluminium phosphate in the course of the 
reactions, and does not impair the transparenc} 7 of the 
lake in oil or ink but softens the texture and makes it much 
easier to work. 

Aluminium hydrate is used pretty largely for certain 
classes of colours which can hardly be termed true lakes. 
Since the colouring-matter is but partially fixed by the 
aluminium hydrate, there is always a large loss of colour, 



LAKE BASES. 65 

but in the case of such products as confectionery colours, 
where the use of other precipitating agents is not per- 
missible for obvious reasons, this property of aluminium 
hydrate of partially fixing colouring-matters is largely 
utilized. 

It is chiefly used in conjunction with other bases, 
because it adds brilliancy and fastness to the pigment, by 
combining with the hydroxy groups ; and for pulp colours, 
because it renders the colours easier to work, removing 
their stiffness and hardness, and, owing to its gelatinous 
nature, retains much water. Alone, aluminium hydrate 
does not give a pigment of much value, since the product 
is lacking in body and opacity. 

The method used for the preparation of the mixtures 
of aluminium hydrate and other bases is to suspend a 
base like China clay in a solution of aluminium sulphate, 
and, while vigorously agitating the mixture, to add slowly 
the sodium carbonate. 

The temperature and concentration of the solutions 
when mixed depend mainly on the consistency and pro- 
perties required of the base ; and it may be taken as a 
general rule that, where small quantities of the hydrate 
are about to be produced, it is not so much that the 
aluminium hydrate is desired' to influence the nature of 
the base, as to assist in the fixation of the colour. It is 
advisable, therefore, to use the solutions fairly dilute and 
not above 45° C. Where proportionally large quantities 
of aluminium hydrate will be produced, it is advisable to 
use rather more concentrated solutions and to precipitate 
at the boil ; otherwise there appears a lack of body in pulp 
colours, and the dry colours are extremely hard, the quantity 
of aluminium hydrate making amends for the diminished 

attraction it has for the colouring-matters. 

5 



66 THE MANUFACTURE OP LAKE PIGMENTS. 

The following proportions have been found serviceable 
as bases for reds, oranges, and greens : — 

For oil colours. — (1) 448 barytes, or lead sulphate. 

„ 25 aluminium sulphate, 17 per cent. 

,, 8*75 sodium carbonate, 58 per cent.. 

45° C. 
(2) 560 blanc-fixe. 
„ 25 aluminium sulphate, 17 per cent. 

,, 8 - 75 soda ash, 58 per cent. 

For pulp colours. — 112 China clay, blanc-rixe, or barytes. 
,, 100 aluminium sulphate, 17 per cent. 

,, 35 soda ash, 58 per cent. 

The aluminium salts of the polybasic acids, such as 
phosphoric and arsenious acids, are largely used in the 
preparation of the lake and base simultaneously, especially 
with strongly basic colours, e.g., magenta, with which these 
acids seem to combine readily to form lakes. The two 
aluminium salts most usually employed for this purpose 
are the arsenite and phosphate. 

The arsenite is prepared by dissolving white arsenic, 
arsenious oxide, As.,0 3 , in a fairly concentrated solution of 
sodium carbonate, by boiling for at least half an hour: the 
solution is then diluted and run into a solution of alumini- 
um sulphate containing the colouring-matter and a little 
sodium acetate. The sodium acetate is used because free 
acetic acid and acid acetates have much less action on 
the base and lake than mineral acids and their acid salts. 
If the precipitation be effected in an acid solution, the 
resultant lake dries very hard and dark, losing all it> 
brilliancy and bloom ; it is very difficult to wash properly, 
and is of so slimy a nature that it is extremely difficult 
to handle. The nature of the precipitate, when formed in 
the presence of an excess of alkali, is entirely different, 



LAKE BASES. <>7 

being quite free from sliminess, and of good body and 
covering power, but, unfortunately, it bleaches many of the 
colours, and with others it prevents precipitation. It is, 
therefore, essential to arrange that the mother liquor of 
the mixture should have an almost neutral or only slightly 
acid reaction, since, if it be but slightly alkaline, in some 
cases, after the colour is used and exposed to air, it deepens, 
ruining the shade. The presence of a small quantity of 
sodium acetate, itself a salt with an alkaline reaction, 
partially neutralizes the acid effect of a very slight excess 
of aluminium sulphate, and produces a better and more 
pleasing result. 

It may be pointed out that when a solution of sodium 
acetate is mixed with a solution of aluminium sulphate, 
partial mutual decomposition takes place, with the for- 
mation of sodium sulphate and aluminium acetate ; and 
on the addition of the alkaline solution there are reasons 
to believe that the sulphuric acid of aluminium sulphate, 
having a stronger affinity for the alkali than the compara- 
tively weak acetic acid of the acetate, is primarily acted 
upon, so that the acid aluminium salt in excess, in all prob- 
ability, is mainly acetate, which has, as previously pointed 
out, a much more feeble action on the precipitate. 

Phosphoric acid, as pointed out in a previous chapter, 
is especially adapted for the precipitation of the violet 
basic colours, and certainly the violet lakes yielded by it 
are very bright, particularly when they are produced on 
a base of phosphate of aluminium. 

The most usual method of procedure is to mix the 
solutions of the colour or colours with a solution of alu- 
minium sulphate, and then to run in a solution of sodium 
hydrogen phosphate, to which has been added sufficient car- 
bonate of soda to produce, on mixing with the aluminium 



68 THE MANUFACTURE OF LAKE PIGMENTS. 

solution, a perfectly neutral precipitate, in accordance 
with the following equation : — 

A1.,(S0 4 ) 3 + 2Na.,HP0 4 + Na.,C0 3 = A1.,(P0 4 )., + 3Na.,S0 4 
+ H.,0 + CO, 

If the solution be either acid or alkaline, there is sure 
to be loss, for, in the first case, the pigment will be very 
gelatinous and slimy, and, in the other, the colour will not 
be by any means completely thrown down. This pre- 
cipitation is best conducted with 10 per cent, solutions at 
the boil ; if stronger solutions be used, the pigment is con- 
taminated w T ith small white lumps, and, if the solutions be 
too weak or too cold, the lake has no body, and retains far 
too much moisture, besides being difficult to handle. 

The phosphates and arsenites of aluminium have thi- 
property of combining with the basic colouring-matters, 
after they have been precipitated. Some makers find that 
they get better results by first of all carefully preparing 
the required salt of alumina, washing it as free as possible 
from all soluble salts, adding the solution of whatever dye- 
stuff is being used acidified with acetic acid, and gently 
raising the temperature, when the colour combines readily 
with the base giving the required result. Either method 
is satisfactory and gives equally good results. The method 
adopted is better determined by the experience of the 
operator. In both these methods the addition of a little 
turkey-red oil in very . dilute solution alter striking, im- 
proves the nature of the lake, but it should not be more 
than about 2 per cent, of the amount of diy lake which 
the batch is expected to yield. 

Phosphates of barium, calcium, and lead are also pre- 
cipitated along with the lake in some instances ; but they 
are not very largely used, and are only of use when match- 



LAZE BASES. 69 

ing a particular shade, since the lakes produced by other 
means are usually superior to them. 

Barium sulphate is very often precipitated together 
with the lake, but this is usually done when mixed bases 
are being used, and when both methods are being used to 
introduce the base into the pigment. It avoids the use of 
too much or rather too great a mass of inert matter which 
is not always easily kept in suspension, especially when 
the substance is a heavy one like barium sulphate, and 
brings about a more intimate mixture of the whole base 
than could otherwise be effected by mechanical means. 
The following example will illustrate the general method 
adopted : — 

1 . A clay, blanc-fixe, and aluminium hydrate base — 

56 parts of China clay, suspended in a solution of 
100 ,, of aluminium sulphate, 17 per cent., treated 

with a solution of 
35 ,, of sodium carbonate, well stirred, the colours 
added, and the requisite amount of barium 
chloride run in, say, 
100 ,, of barium chloride. 

By the addition of the sodium carbonate to the alu- 
minium sulphate solution containing the clay, the alu- 
minium hydrate formed is more thoroughly incorporated 
with it than it would be by any merely mechanical admix- 
ture. On the addition of the barium salt, the barium 
lake is formed, and, at the same time, the excess of barium 
combines with the sodium sulphate formed on the de- 
composition of the aluminium sulphate, giving barium 
sulphate, or blanc-fixe. 

This example illustrates very well the reason why 
pigments produced by this and similar methods are clearer 



70 THE MANUFACTURE OF LAKE PIGMENTS. 

and brighter than those simply precipitated on inert bases ; 
for, however well the mixture may be agitated during 
precipitation, in such cases the pigment consists of the 
inert base fully or partially coated with the lake and free 
lake particles. In such a method as described above, the 
China clay is practically coated with the gelatinous pre- 
cipitate of aluminium hydrate, which retains a considerable 
amount of the sodium sulphate, and often, on the addition 
of the colour, partially combines with it as well as exert- 
ing its natural property of absorption : therefore, when the 
barium chloride is added to the mixture, the formation of 
the lake and of barium sulphate takes place in the particles 
of the suspended colouring-matter as well as in the 
thoroughly incorporated mixture produced by the reaction 
of the colour, barium chloride, and sodium sulphate. 

In Plate III are shown a series of shades produced by 
acid dyestuli's by barium chloride on the clay or blanc- 
hxe and alumine base : — 

Xo. 1 shows Acid Yellow 79210 (Brit. Dyes). 



Xo. 


2 , 


Metanit Yellow 


Xo. 


3 . 


Citronine E 


No. 


4 . 


Orange YVH 


Xo. 


5 . 


. Scarlet E 


Xo. 


6 . 


Scarlet 3 E 



Examples of these mixed methods might be shown for 
each class of colouring-matters, and yet none be given t< i 
meet some special and individual case. It is by far the 
best plan for each colour-maker to examine carefully the 
colour, and to devise for himself the most rational way of 
^producing the best result ; and, b}' adopting those bases 
which he knows from experience to be most suitable for the 
purpose for which the pigment is required, to experiment 



PLATE III 



Manufacture of Lake Pigments 



To face page 70 



LAKE BASES. 71 

until he arrives at the most satisfactory result. What 
works well in one man's hands in a certain place does not, 
owing to differences of method and appliances, work well 
with another man in another place, and it is as well to 
work out personally those methods most suitable to the 
conditions under which the maker labours. 

In conjunction with the use of aluminium hydrate 
bases, especially with colours that give better results when 
the solution of the dyestuff is added in slightly acid solution, 
improvement in the texture and nature of the base have 
been obtained by using phosphoric acid in place of acetic. 

The pure ortho- variety is now easily obtained, of a 
specific gravity varying from 1250° to 1750°, the weaker 
strength being the cheaper. It can be obtained free from 
even traces of iron, is not a dangerous acid to use, and, 
in conjunction with colouring-matters containing amido, 
hydroxy, and sulphonic-acid groups, has a tendency as 
phosphate of aluminium to brighten the shade and improve 
its fastness generally. 



CHAPTER VII. 

THE PRINCIPLES OF LAKE FORMATION. 

An examination of the constitution of the artificial colours 
and the methods adopted to form lake pigments from them 
shows that the latter is effected by combining the colours 
with metallic or various acid bodies, both organic and in- 
organic ; in other words, the formation of salts, in which 
the colouring-matter plays the part of the acid or base. 

In order, therefore, to consider the general principles 
to be followed in the production of lake pigments from 
artificial colours, it is necessary to divide them into four 
classes — 

I. Purely basic colours. 

II. Purely acid colours. 

III. Compound colours of both an acid and basic nature. 

IV. Azo colours. 

The basic colours are those containing aniido or sub- 
stituted ammonia groups, either simply, or in such position > 
and preponderance over weak acid groups that the acid 
functions of such groups may generally be regarded as 
negligible from a lake-forming point of view. 

The acid colours include a much larger number of 
lake-forming groups, namely, the hydroxy, nitro, carboxyl, 
and sulphonic-acid groups — one or more of which may 
occur in the same colour molecule, together with a lake- 
forming group of a basic nature. 

It is necessarv to consider carefully the method of 

(72) 



THE PRINCIPLES OF LAKE FORMATION. 

procedure to be followed where the lake-forming group 
<>r groups in a colouring-matter are of a simple nature, 
capable of forming simple lakes readily, and where the 
colouring-matters are of a more complex constitution, 
containing several groups, giving satisfactory results only 
when compound lakes are formed from them, though they 
are often capable of being thrown down by the action of 
some reagent on one or more similar groups. 

The production of lakes from artificial colours cannot 
be regarded as the mere precipitation of a colouring-matter 
on a base to form a lake, for almost all colouring-matters 
are insoluble in strong solutions of common salt, yet the 
precipitation of such a colour by common salt on an inert 
base produces but a mechanical mixture of the colour and 
the base from which the colour can be redissolved un- 
changed. A lake pigment must be regarded as a chemical 
combination of the dyestuff with one or more bodies, con- 
ferring on it pigmentary qualities, and in most cases giving 
a body of the type of the original colour, but of a different 
chemical composition. Whether these combinations are 
of the nature of simple exchanges, the reactions being 
capable of expression by simple chemical equations, is a 
very debatable point. In some cases experimental data 
indicate such simple changes, but in others the present 
knowledge of the actual constitution of the pigment is a 
very open question. 

When a solution of a dyestuff, more particularly the 
basic colours, is added to starch, clay, etc., a certain 
amount of colouring-matter is taken up. This cannot be 
accounted for by any chemical attraction of these various 
bodies for the colouring-matter, but it may be due to 
partial dissociation of the colouring-matter producing the 
free colour acid or base, which is attracted to and adheres 



74 THE MANUFACTURE OF I.AKK PIGMENTS. 

to the particles of the insoluble matter present in the 
mixture. This is most evident in the case of weak bases 
combined with weak acids. Though the cause of this 
seeming absorption cannot be clearly elucidated, there can 
be no doubt that the colouring-matter in such a pigment 
cannot be looked upon as a true lake, but simply as an 
intimate mixture of insoluble matter and uncombined 
colouring-matter ; and the extremely fugitive properties of 
such coloured bodies to air and light, as well as their want 
of fulness and brightness, confirms this idea, prompting 
one to condemn entirely such methods of producing colours 
and styling them lakes. 

This apparent absorption of colouring-matter may also 
be the property of a true lake ; for many colours, especially 
those of a basic nature, often require but a tithe of the 
precipitating agent to entirely precipitate them that an ex- 
amination of their formula would lead one to think would 
be required. For instance, a molecule of magenta requires 
theoretically a molecule of tannic acid, but it can be almost 
entirely precipitated by about a third of that quantity. It 
is scarcely conceivable that the addition of tannic acid 
leads to a rapid dissociation of the magenta molecule, 
though perhaps the tannic acid and magenta compound 
may possess considerable attraction for the free colour 
base ; but the compound produced by tannic acid, which 
is trihydroxy acid, may possess the property of taking up 
or being dyed by the uncombined soluble salt of magenta, 
and thus cause the seeming absorption of the rest of the 
colour. Where the full amount of tannic acid is used, the 
lakes are more permanent, but not so bright as those in 
which only the minimum quantity has been employed. 
The plan of using but the necessary quantity of tannic acid 
in these cases to secure greater brightness has obtained for 



THE PEINCIPLBS OF LAKE POEMATION. /•> 

the tannic acid lakes a reputation for being far more fugi- 
tive than they really are, and has resulted in their being 
ranked but little faster than the fugitive lakes produced 
by such acids as arsenious and phosphoric. In point of 
fact they are the most permanent of all the lakes produced 
from basic colours. 

Where a colouring-matter contains several lake-forming 
groups, which are capable of entering into combinations 
with various reagents, the full value of the chromogenic- 
power and the most satisfactory and permanent results 
are obtained when as many as possible of such groups are 
combined with those bodies for which they have an affinity. 

A very good example of this can easily be demonstrated 
by a colour such as concentrated Acid Green D (M. L. & B.) , 
which yields fairly fast green lakes by precipitation on 
aluminium hydrate with barium chloride. The precipita- 
tion is almost complete, but an appreciable amount of colour 
remains in solution ; or, more correctly expressed, the simple 
barium lake is soluble in water, giving the impression that 
the whole of the colouring-matter is not thrown down. 
If, previous to the addition of the barium chloride, tannic 
acid be added to the solution of the colouring-matter the 
precipitation is complete, and a much faster, brighter, and 
more insoluble product is obtained. The improvement 
in the properties of the lake by this addition is not due 
to any action of the tannic acid per se : but, as the colour, 
Acid Green D '(Cone.) is an amido-sulphonic acid, the 
amido or basic properties are in the first place satisfied by 
combination with the tannic acid. The latter reagent has 
not the power alone to form a lake from such a strongly 
acid colour, therefore no precipitation or very little occurs 
until the addition of the barium chloride, which, combin- 
ing with the sulphonic acids, throws down the barium 



r(i THE MANUFACTURE OF LAKE PIGMENTS. 

tannic acid lake of the colour in which the affinity of th< j 
various lake-forming groups has been completely satisfied, 
giving in consequence a more stable body, and developing to 
a much greater extent the colouring power of the dye-stuff. 

It does not follow because a colouring-matter contain - 
lake-forming groups that it is capable of being converted 
into a pigment, for the properties of the ordinary combina- 
tion which precipitates a similar colour may differ, just as 
the chloride of silver is insoluble and the chloride of sodium 
extremely soluble ; or the groups themselves may be so ar- 
ranged in the colour molecule, and be so opposite in char- 
acter, though capable of being used for application to textile 
fibres, that they cannot by any means, simple or compound, 
be precipitated satisfactorily as a lake pigment. A good 
example of such a colour is acid magenta, a triamido- 
sulphonic acid. 

The formation of lakes from basic colours is dependent 
on the combination of the amido or basic group or groups 
in the colour molecule with various acids, producing in- 
soluble salts of the colouring-matters. 

In the majority of cases the lake is produced together 
with the whole or part of the base, ensuring the presence 
of an excess of the precipitating body since the reaction is 
brought about by precipitating the insoluble metallic salt, 
together with the insoluble salt of the colouring-matter. 
Such methods may be regarded as the precipitation of an 
ordinary mixture. But, as has already been remarked, 
the lakes produced in this way from phosphoric, arsenious, 
palmatic, resinic acid, etc., though very bright, are very 
fugitive, and often extremely poisonous. Their manufac- 
ture is a matter of great simplicity when due care is paid 
to the chemical properties of the various compounds used 
in their production. 



THE PRINCIPLES OF LAKE FORMATION. 77 

The most permanent lakes produced from basic colours 
are the tannic acid lakes, which, though duller even when 
correctly prepared, are much more permanent than the 
lakes produced from these colours by other means. A 
magenta salt, e.g., the hydrochloride, gives a tannic acid 
lake as follows : — 

/C, ; H 4 NH 2 
G — C t .H 4 NH, when converted into 

\C H 4 NHHC1 



/C (i H 4 NH., C,H.,(OH) 3 COO 

— c, ; h 4 nh.; 

\C, 5 H t NHHOOC (HO),H,( 



the tannate gives — C — C ( H 4 NH." 



This salt is soluble in the hydrochloric acid liberated, 
and although almost complete precipitation is obtained if 
an excess of acetate of soda be added before the tannic 
acid, or by using tannate of soda, such lakes are very dull, 
and their permanency but little better than the lakes of 
other acid bodies. The full value of tannic acid is only 
shown when it is used in conjunction with a salt of 
antimony, preferably tartar emetic, which, as it is a 
tartrate, is able of itself to combine with the basic colour- 
ing-matter, although in but few instances are the precipi- 
tates insoluble in hot water. When tannic acid is added 
to the mixture in presence of sodium acetate, the whole of 
the colour is precipitated as a double antimony and tannic 
acid lake. The latter, though not as bright as the arsenious 
acid lakes, is much brighter and far more permanent than 
those produced from tannic acid or tannate of soda. 

The determination of the exact amount of tannic acid 
to be used with each individual colour is a matter of con- 
siderable difficulty, for it has been shown that, though 
in many cases the amount of tannic acid theoretically 



(S THE MANUFACTURE OF LAKE PIGMENTS. 

required for a pure colour is more than sufficient to pre- 
cipitate the colouring-matter, whether it be all thrown 
down as a lake is a matter of considerable doubt, in- 
creased by its physical behaviour. Where the theoretical 
amount is used, a much faster, though, at the same time, 
duller lake is produced. No reliable data can be obtained 
by simply titrating solutions of the dyes with tannic acid. 
If an excess of tannic acid be used, it greatly interferes 
with the working of the colour, besides increasing the cost 
to no purpose, but where the constitution and the purity 
of the colour employed are approximately known, it is by 
far the wisest plan to use the- theoretical amount. Hence 
it is very important in making lakes from basic colours 
to use those brands which are commercially pure, and 
whose chemical nature and constitution are known. 

Various researches have shown that a molecule of 
tannic acid is fixed by about half a molecule of tartar 
emetic, though from an examination of the two bodies it 
would have been surmised that a molecule of tannic acid 
would have required a molecule of tartar emetic. This is 
borne out in practice, since if, previous to the addition of 
tannic acid, this proportion of tartar emetic be added to the 
mixture, complete precipitation takes place ; and in cases 
where the exact constitution of the colouring-matter can- 
not be ascertained, and an excess of tannic acid is used, it 
is advisable to maintain this proportion, so that the in- 
jurious effects produced by an excess of these reagents is 
reduced to a minimum. The tannic acid and tartar emetic 
not required to combine with the colour are precipitated 
as a compound salt of antimony. Therefore, in producing 
lakes from basic colours, wherever possible tartar emetic 
and tannic acid should be used, and, in order to obtain 
the best results, the molecular ratios between the colouring- 



PLATE IV 



■■ 




1 




^^1 


1 ■ 


■ 













Manufacture of Lake Pigments 



To face page 78 



THE PBINCIPLB8 OF LAKE FORMATION. i l .) 

matter and the two lake-forming bodies should be main- 
tained. 

The conclusion to be drawn, therefore, is that for tannic 
acid lakes it is advisable not to precipitate them simply as 
tannates of soda, but to combine them with some double 
salt of tannic acid, such as that formed by the combination 
of tannic acid and tartar emetic. For special shades and 
tones the tannic acid compounds of iron and tin are of 
great service, but on account of the reducing action of 
stannous chloride great care must be exercised in using 
this reagent. 

Plate IV shows a series of shades produced by means 
of Tartar Emetic and Tannic Acid by basic dyestuffs : — 



No. 2 



No. 1 shows Auramine (Brit. Dyes), 

f Auramine „ ,, 

I. Malachite Green Crystals „ ,, 

No. 3 ,, Malachite Green Crystals ,, ,, 
No. 4 „ Methylene Blue 2 B 

No. 5 ,. Methyl Violet 2 B ,, 

No. 6 ,. Magenta Crystals ,, „ 

The lake-forming groups in the acid colouring-matters 
are more numerous, and require various methods for their 
precipitation. 

The property that basic and acid colouring-matters 
have of combining with each other is utilized in tinting 
colours to various shades. Though perhaps the result of 
such combinations leads to the ready production of the 
required shade, such means should only be used with 
great discrimination, for such combinations often readily 
dissociate, and give by no means permanent pigments. 
It is far better, where practicable, to combine each colour 
with its typical lake-forming compound. 



80 THE MANHAi TUBE OF LAKE PIGMENTS. 

The property of purely amido salts of combining with 

amido-sulphonic acids has been made use of in the pro- 
duction of pure lakes from such colours as Alkali I31ue and 
Victoria Blue, having a strong staining colour with a high 
bronze suitable for replacing Chinese Blues in the manu- 
facture of lithographic inks. The method of procedure 
will be dealt with in the chapter dealing with blue lakes. 

Of the acid colours, the nitro derivatives are perhaps 
least used, because their metallic salts are usually extremely 
soluble. The few combinations with the oxides of the 
heavier metals are not of such a nature as to be esteemed 
as pigments. 

The hydroxy group is a powerful lake-forming group, 
which occurs in those colours from which the fastest, most 
permanent lakes are produced, yet its value as a lake- 
forming group is not great in the monohydroxy compounds, 
but only in those where it occurs as a dihydroxy derivative. 

The position of the hydroxy groups in the molecule 
exerts considerable influence on the lake-forming properties, 
for, unless the hydroxy grouos be in the ortho-position in 
respect to each other, the lakes produced are not fast, but 
mav be reckoned among the most fugitive, e.g. the eosines, 
which are metahydroxy compounds. The alizarines, 
orthohydroxy compounds, yield the fastest of all lakes. 

The lake-forming bodies for the orthohydroxy com- 
pounds are the oxides of aluminium, chromium, and iron, 
which can play the part also of weak acids under certain 
circumstances. The lakes produced from alizarine by alu- 
minium alone are by no means so brilliant as when calcium 
salts also enter into the lake-forming reactions. The exact 
nature of the lake formation with these dyes cannot be 
definitely stated, but it is to be inferred that the calcium 
and aluminium combine, with the aid of the oleic acid 



THE PBINOIPLBS OF LAKE FORMATION. 81 

which must be present to yield satisfactory results, yield- 
ing finally a calcium aluminium salt of the hydroxy colour- 
ing-matter. Aluminium lakes are those usually met with, 
but the corresponding lakes of both iron and chromium are 
of great permanency and value. The colouring-matters con- 
taining the carboxyl group, which may be regarded as an 
allied hydroxy group, yield but few colours which are used 
in the production of lakes. When present in the molecule 
with other hydroxy groups, and if these be in the ortho- 
position either in respect to themselves or the carboxyl 
group, these allied hydroxy groups possess the same 
properties as regards lake-formation as the diorthohydroxy 
dyestuffs. 

When combined with several amido groups, the carboxyl 
group can generally be disregarded, and the colour treated 
as an ordinary basic colour. If both amido and hydroxy 
groups, as well as the carboxyl groups, or if the hydroxy 
groups, or a hydroxy and a carboxyl. group, be in the ortho- 
position, the colour will be found to possess properties 
similar to those of the alizarines. 

The sulpho group, which, like the carboxyl group, 
possesses no chromogenic powers, is found in the dye-stuffs 
together with hydroxy, carboxyl, and amido groups, both 
singly and in mixtures. 

The sulphonic-acid group confers powerful acid pro- 
perties on the colouring-matters, quite overpowering the 
basic properties of amido groups when they occur in the 
molecule, and greatly increasing the acid properties of other 
acid groups with which it may occur. 

The increase in the number of sulphonic-acid groups in 
the molecule of a colour does not increase its lake-forming 
power, but the position of the sulphonic acid in the colour 
molecule has a very considerable influence on the lake- 



82 THE MANUFACTURE OF LAKE PIGMENTS. 

forming capacity. Similar compounds prepared on the 
same lines, but with the sulphonic acid group in different 
positions, show marked differences in their behaviour with 
lake-forming bodies ; and it must be concluded that the 
reason why many colouring-matters which apparently 
should yield lakes easily by combining the sulphonic-acid 
group with barium oxide, do not yield satisfactory results 
in practice, is because the intramolecular relationship is of 
such a character as to interfere with satisfactory lake for- 
mation. What these various relations are has not been 
studied, so that the constitution of the sulphonated dyestuffs 
used in lake-making should be carefully examined, and 
their behaviour with precipitating agents, and their reac- 
tions with acids and alkalies, both before and after lake 
formation has taken place, accurately noted. 

The typical lake-forming body for the sulphonic-acid 
groups is barium oxide. Many of the oxides of other 
metals often precipitate more completely the colouring- 
matter, but the lakes lack both the brilliancy and perman- 
ency of the barium lakes. 

The Hijdroxij-sulphonic Acids. — The introduction of the 
sulphonic-acid group into a compound containing hydroxy 
groups. If these groups be not in the ortho-position in 
respect to each other, the weak lake-forming power of the 
hydroxy groups can be entirely overlooked, and lake forma- 
tion takes place only in the sulphonic-acid groups. If, how- 
ever, they be in the ortho-position, as in alizarine S, alizarine 
sulphonic acid, it will be found that, unless the hydroxy 
groups are combined as well as the sulphonic acid, the 
lakes produced are fugitive and lack the full development 
of the chromatic power of the colouring-matter. Since 
aluminium and allied oxides and hydrates are the lake- 
forming bodies for these groups, the aluminium barium 



THE PEINCIPLES OF LAKE POEMATION. 83 

lake must be prepared, and the combination of one instead 
of both the lake-forming groups of the colouring-matter 
effected, otherwise the result is generally useless for pig- 
mentary processes. 

Although lake formation in dyes other than those in 
which the hydroxy groups are in the ortho-position may 
be, as a rule, disregarded, it is to be remarked that when 
the barium lake is formed in the presence of aluminium 
hydrate the resultant pigment is brighter and more per- 
manent. 

The introduction of the sulphonic-acid group into a 
basic dyestuff converts it into an acid dye, but it cannot 
be assumed that the lake-forming properties of the amido 
group are destroyed, for it will be found that the stronger 
the basic properties of the sulphonated base, the more 
difficult will it be to produce simple barium lakes from it. 
This difficulty is not solely dependent on the basic pro- 
perties of the sulphonated colour base, but is often in- 
fluenced by the molecuiar arrangement of the various 
groups. 

It will be found that after the formation of the barium 
lake the basicity of the colour base again comes to the 
fore, and, unless this is also satisfied, the pigment produced 
will be found wanting in purity of tone and colour; in 
these cases, the only satisfactory lake-forming material to 
use is tannic acid, which develops the full beauty of the 
shade. 

Though these dyes may be acid colours for the purpose 
of dyeing, when they are converted into the barium lake, 
which may be partially or wholly soluble, they must then 
lir regarded as purely basic colours, and treated accord- 
ingly. 

Basicity due to the presence of an amido group in a 



S4 Till: MANUFACTURE OF LAKE PIGMENTS. 

sulphonic acid colour, of which the colour base possesses 
but very weak basic properties, as in the case of the hy- 
droxy-sulphonic acids, in which the hydroxy groups have 
little or no lake-forming properties, often in these cases also 
loses its lake-forming power, and can then be disregarded : 
but in all cases where it, i.e., the basic lake-forming power, 
evinces itself, it must, if the best results be desired, be 
combined as well as the sulphonic-acid groups. 

When hydroxy as well as amido groups possessing lake- 
forming properties are present in a colour molecule, it 
is often difficult to produce satisfactory lakes from such 
colours by means of tannic acid and barium chloride, 
because the hydroxy group, being uncombined, often 
renders the barium tannin lake soluble, and hence useless 
as a pigment; and unless the hydroxy group is combined 
by the use of an oxide or hydrate, with which it is capable 
of entering into combination, unsatisfactory results are 
only to be looked for. The hydrates of barium and calcium 
are most useful for this purpose. 

Where a carboxyl group occurs together with both 
hydroxy and amido groups in a sulphonated colouring- 
matter, and the hydroxy and carboxyl groups are in the 
ortho-position, it will usually be found that the lake-form- 
ing property of the basic group will have disappeared : 
therefore, after the formation of the barium lake, the dye- 
stuff may be regarded as an ortho-hydroxy-carboxyl com- 
pound, and the compound lake must be produced by the 
means already discussed for such compounds. 

The Azo 'Pigment Colours. — These, of themselves, can- 
not really be classed as lake colours ; they are definite com- 
pounds formed by combining an amido compound with 
some suitable phenol by azotizing. They are very highly 
coloured bodies, of great staining power, and, like Prussian 



THE PRINCIPLES OF LAKE FORMATION. 85 

blue, capable of being let down very considerably to form 
useful pigments. In some cases they can be used as pig- 
ments without any dilution. Many of these come into 
the market as the mono-sulphonic acids in combination 
with sodium, which the lake-maker simply substitutes by 
barium, calcium, zinc, or lead, according to the particular 
shade he requires. 



CHAPTEK VIII. 

RED LAKES. 

The various red shades of lake pigments derived from 
artificial colours vary from very yellow shades of scarlet to 
deep maroon. The colours from which they are formed 
belong to both the acid and basic dyes. The basic dyes 
belong principally to — 

I. The triphenyl-methane colours, of which Magenta and 
Khodamine are typical examples. 
II. The azines, which are represented by the various brands 
of the Safranines. 
The chief groups to which tne acid colours belong are — 

I. The azo colours, such as Scarlet 3K, Ponceau GL, Fast 
EedO. 
II. The triphenyl-methane colours ; for example, Eosine 

Phloxin. 
III. The oxyketone colours, to which the Alizarine colours 
belong. 

The most important of the red basic colours is magenta 
which is used not only alone to form lakes of a magenta- 
red shade, but with acid scarlets and reds to produce 
various shades of red. It is not of much use in modifying 
the shade of violet lakes, since its own pronounced shade in- 
terferes with the shade of the mixed colour lake, giving to 
it a harsh, unpleasing tone. The same fault also prevents 
it being used to shade eosine lakes, for which purpose the 

rhodamines, or rose Bengale, is to be preferred. 

(86) 



RED LAKES. 87 

The brightest and most pleasing magenta lakes are 
those produced by combining the colour with arsenious or 
resinic acid. The tannic acid lake alone is not of any real 
value, being as fugitive as the arsenious acid lake, besides 
being very much duller. The tartar emetic and tannic 
acid lake is much more permanent, but not so bright as 
the arsenious acid lake, and though it is little in demand, 
on account of its inferior brilliancy, it has considerable use 
as a shading matter in producing the best qualities of 
maroon lakes. There is little to choose between the 
various brands of good magentas put into the market by 
the various firms ; but it is advantageous to select a good 
crystallized variety and use it, and it alone, in all cases 
where a magenta is required. The rubin small crystals 
of the Berlin Company is about as good a one as there is 
in the market, though it is quite equalled by the produc- 
tion of other makers. 

The rhodamines, of various brands, such as Khodainine 
B, G, S, 6G, 12G, yield from bluish-red lakes to reddish- 
pink. When prepared alone, without admixture with 
other colours, it is by far the best plan to make the tartar 
emetic and tannic acid lakes, for lakes produced from any 
of these colours are extremely fugitive, and if the colour 
is wanted to stand the action of light at all, the tannic 
acid and tartar emetic precipitation is the only one which 
can be recommended. These lakes when prepared for 
calico printing should be made at the boil, and, after 
washing free from various salts, should bs treated with a 
hot solution of 0'5 per cent, olive-oil soap at SO ('. The 
colours do not bleed, but the pigment then gives better 
results when printed. The best base to use is a tine 
quality of blanc-fixe. 

The extra brand of the colour should alwavs be used 



88 THE MANUPACTUBE OF LAKE PIGMENTS. 

when obtainable ; though it is much dearer, it is more 
economical in the long run. 

These colours, i.e., the rhodamines, are largely used for 
tinting violets; they are then precipitated with phosphoric 
acid or its salts. They are very powerful colours ; a very 
small percentage, in the mixed colouring-matters, of a 
strong colour like Methyl- Violet B is sufficient to change 
the shade to a bright purple. It will be found that many 
of the red shades of violet are reddened merely by the 
addition of magenta. In lakes this does not give such 
pleasing shades as are given by the rhodamines, and it is 
advisable to use a pure methyl violet as the principal 
colour and to tone it with rhodamines. These colours are 
more expensive than the magentas, but, especially for sur- 
face paper-work, the shades given are much more attrac- 
tive. 

The rhodamines combine very readily with eosine, and 
when. mixed with the eosine before precipitating with lead 
acetate, they blue the shade of the cheaper and yellower 
eosines, giving shades corresponding to those of a higher 
halogen, and, therefore, more expensive brand. In this 
conjunction the eosine and the rhodamine must be dis- 
solved separately, and the rhodamine solution should be 
very dilute, otherwise there is risk of the two colours 
combining together in small specks, often so minute as 
not to be visible until the pigment is in use, as a very 
diluted tint, when the whole of the surface is covered with 
minute streaks. 

The basic red colouring-matters of the azine group are 
represented by the various brands of safranine, which give 
a magenta-like lake, but one of a much faster and redder 
tone. 

The onlv lakes of the safranines which are at all to be 




RED LAKKS. 

recommended are those prepared from tartar emetic and 
tannic acid. These are much brighter than the corre- 
sponding magenta compounds, and, for purposes where 
superior fastness is required, are to be recommended. 
These colours are also of great value in making maroon 
lakes, since they do not give colours which blacken so 
readily when heated at 100° C. as those produced by 
magenta, more especially so when the basic colour is fixed, 
and not merely carried down by the acid colour. 

For the safranines, as well as for all other tannic acid 
and tartar emetic lakes, the most suitable base is blanc- 
fixe. The safranines have also a considerable use, when 
precipitated as the resinate of aluminium, zinc, and lead, 
in stencilling inks and tin printing, since the shades are 
fairly fast to light and very bright. Also they lend them- 
selves very readily to this form of precipitation. Recently 
they have been replaced by Ciba Bed, which, though 
somewhat duller, is very much faster to light. 

Coming to the azo group, it has been thought advisable 
to deal with the insoluble azo colours known as the pig- 
ment colours, such as Helio Fast Red RL, Pigment Red 
R, and the simpler sulphonic acids of similar compounds, 
e.g., Lake Red P, Lithol Red G- and R, in the chapter 
dealing with the production of insoluble azo colours in the 
form of pigments, since the preparation of these colouring- 
matters for the market is practically a branch of the in- 
dustry by itself, and the methods applicable to the ordinary 
hydroxy-sulphonic acids of the azo group are not suitable 
to them. 

The red colouring-matters of the azo group are very 
numerous, and the number at the disposal of the lake- 
maker often causes the use of a very large number of 
brands, with resulting hesitancy in selecting colours to be 



90 THE MANUFACTURE OF LAKE PIGMENTS. 

used to obtain a lake of a given shade. But the choice 
of colours should be strictly limited in practice ; it is far 
better to obtain a shade by the judicious blending of a f<w 
scarlets or reds, than to buy for each separate lake a 
separate colour from which to produce it. Almost all 
shades of red and maroon produced from this colour can 
be obtained from a range of four to eight shades, i.e., four 
cheap and four better shades for the various classes of 
work, and the shades required may be classified -as fol- 
lows : — 

I. A yellow shade of scarlet. e.</.. Ponceau 4GBL. 

II. A medium shade. e.g., Ponceau GL and Pone au GE. 

III. A blue shade, e.g.. Scarlet 3R, Ponceau 4R. 

IV. A deep blue shade, euj., Fast Red O. 

The colours mentioned are but examples of many that 
are equally good and of similar shades and properties. In 
selecting a series of azo colouring-matters, attention should 
be paid to the following points : — 

I. The brilliancy and permanency of the pigment pro- 
duced. 
II. The colouring power of the dyestuff. 

III. The insolubility of the pigments made from them in 

water. 

IV. The complete precipitation of the colouring-matter. 

The scarlets produced by the British manufacturer are 
fully equal to those of the continental firms. 

Plate V shows a series of fairly wide range of acid 
scarlet dyestuflfe which produce good lakes, these lakes 
are the barium lake on the clay or blanc-fixe alumina 
base : — 




Manufacture of Lake Pigments 



To face page 90 



RED LAKES. 91 

No. 1 shows Scarlet 2RG (American). 

No. 2 ., R (Brit. Dyes). 

Xo. 3 .. , 2R 

No. 4 .. ., 3R 

No. 5 .. 5 % 4 .. 

No. 6 .. ., 5 7 c 4a ., 

Turning to the consideration of the constitution of the 
colouring-matters, the hydroxy-sulphonic acids are to be 
recommended. The more complicated azo-diazo colours 
obtained from benzidine, including the class of direct dye- 
ing cotton colours, yield very good lakes ; but, all things 
considered, the lake produced from the hydroxy-sulphonic 
acid colours are to be preferred, for, not only are they more 
permanent to light, but they are much more easily con- 
verted into pigments, and are as a rule much cheaper. 

When using hydroxy-sulphonic acid colours, the best 
base is one containing aluminium hydrate, since the shades 
produced are much clearer and brighter when this body 
is present. If it does not enter into combination with 
the colour, it renders it much brighter and more stable. 
To give greater body, almost any inert material used as 
a base for lakes may be used, barytes, blanc-fixe, clay, 
etc. ; but it is advisable to produce the aluminium hydrate 
in presence of the other members of the base, since it 
is then thoroughly incorporated with them, and a homo- 
geneous base is the result. 

The precipitating agent to be used for the majority 
of the azo-sulphonic acids is barium chloride. Soluble 
salts of lead very often give more complete precipitation, 
but the shades are much duller ; the lead salts are much 
dearer than those of barium, besides being more, readily 
changed by the action of air and light. 

The best method of producing pigments from this class 
of red dyestuffs is by simultaneous precipitation with 



*)2 THE MANUFACTUBE OF LAKE PIGMENTS. 

barium sulphate or blanc-fixe, on a freshly prepared 
aluminium base, by means of barium chloride. 

Lake pigments produced from a single colour will 
usually be found to have a bluish cast and lack bril- 
liancy. This is best remedied by taking a colour which 
yields a lake of a much bluer shade than the shade re- 
quired, and mixing it with a little orange dyestuff of a 
similar chemical nature, and precipitating in the usual 
way. It is desirable in this case, if the most fiery effects 
be required, to dissolve the colours together, for if they 
are dissolved separately, and then added to the tank, a, 
slightly duller shade is the result. This also holds good 
as regards all the mixtures of these colours, whether they 
be reds or oranges. In the production of compound 
shades such as maroon, where basic colours are used, it is 
usual where the basic colour is not converted into a lake, 
but is merely carried down by the pigment formed from 
the acid-azo colour, to add the solution of the basic colour 
immediately after the addition of the colour to the base 
and before precipitation. On no account should basic 
colours and acid colours be dissolved together, for the 
result is usually disastrous, owing to the formation of a 
black or deeply coloured tarry precipitate. 

In the production of the better sort of maroon and 
similar lakes, the magenta is introduced as a pigment. 
This is done by adding it to the base, and precipitating 
the red colouring-matter in the usual way. 

For the production of maroon shades, basic brown 
(usually Bismarck Brown), magenta, and safranine are 
used to give the barium lake of the azo-scarlet the desired 
shade. The deeper the shade of maroon required, the 
deeper the shade the azo-red should be ; but if such a 
colour as Fast Ked (M. L. & B.) be used alone, the shade 



RED LAKES. 93 

lacks brilliancy. It is therefore advisable always to use a 
proportion of bright scarlets in the mixture used for the 
production of maroons. 

Maroon shades, made by utilizing the property pos- 
sessed by acid colours of combining with basic colours, are 
much more fugitive than those in which the basic colour 
is introduced in the form of a pigment, and, as mentioned 
before, they have a tendency when dried at 100° C. to 
turn much deeper and blacker, losing all the bloom which 
such colours usually possess. 

The acid red colouring-matters of the triphenyl-methane 
colours comprise mainly the eosines and allied colours. 
They are h) r droxy colours. The hydroxy groups are not 
in the ortho-position in respect to each other, being usually 
in the different phenyl rings. They readily combine with 
the oxides of lead, zinc, aluminium, tin, etc., producing 
fugitive lakes of great brilliancy and staining power. The 
shade of the pigment produced is dependent on the metallic 
salt used in their production, lead salts giving the bluest, tin 
and aluminium much yellower shades. Barium salts do not 
react with those colours in a satisfactory manner, and the 
barium lakes are never prepared. The eosines, etc., all con- 
tain a large number of halogen atoms in their constitution, 
which probably influences to a great extent their attraction 
for the various metallic oxides, though the halogens them- 
selves take no part in the formation of the lake pigments. 

Of the eosines there are several brands — nearly even 
maker having a different name for the same compound, 
which, however, differ a little in the shade produced when 
made into lakes. For instance, a 5 per cent, lake on blanc- 
fixe made from Eosine A (of B.A.S.F.) differs somewhat 
from a 5 per cent, lake made from Eosine Yellowish (Ber), 
yet both are salts of tetrabrom-fluoresceine. 



94 THE MANUFACTUBB OF LAKE PIGMENTS. 

Rose Bengale and the Phloxines are mixed halogen de- 
rivatives of Fluoresceine, which are rather expensive, but 
yield very bright and pleasing shades, of a much bluer 
cast than the Eosines proper. The introduction of iodine 
into the molecule tends to blue the shade of an Eosine, and 
many firms style the bluer shades of the fluoresceine 
colours Erythrosines. As a rule, these bluer shades are 
much more expensive than the yellower shades, which 
contain bromine or chlorine, and their price prevents the 
lake-maker using them. The method which is generally 
adopted to raise the shade of an Eosine is to add a little 
Rhodamine to the mixture of Eosine and base before pre- 
cipitation ; the Eosine combines with the basic Rhodamine, 
and the two colours are carried down together. In this 
case there is no advantage to be gained by using a pigment 
of Rhodamine, since the Eosine pigments themselves are 
so extremely fugitive. 

The precipitation or production of eosine lake pigments 
is usually carried out either by lead, tin, zinc, or aluminium. 
They form the colouring-matter in vermilionettes and 
similar colours used largely for paint, and for this purpose 
are usually precipitated by lead acetate on barytes, lead 
sulphate, red lead, or mixtures of these bases. For 
paper-work and pulp colours, aluminium, tin, and zinc are 
used. Where an inert base is used, blanc-fixe is the only 
one really suitable ; but mixed aluminium hydrate bases 
are largely used when aluminium and tin are used as pre- 
cipitating agents. 

Eosines, above all colours, are readily affected by the 
precipitating agent, and show very marked differences in 
appearance on the various substrata on which they may 
lie thrown down. 

Basic lead acetate gives the most perfect precipitation. 



RED LAKES. 95 

Normal lead acetate is almost as good, but gives a yellow 
shade, as might be expected ; zinc salts give a light dullish 
blue tone, and the aluminium precipitation is the yellowest 
of all. The whole of these dyestuffs are very sensitive to 
acids, turning yellow at once with free mineral acids, and 
developing much bluer tones in the presence of alkalies. 

The coarser the base the deeper and richer the pig- 
ment appears to be. On barytes and orange lead a very 
small percentage of colour gives a very lull shade, whereas 
double the amount on precipitated lead sulphate or blanc- 
fixe is pale dull and chalky in appearance. 

The selection of the brand of eosine to be used is a 
matter of some difficulty, since their prices vary from about 
three shillings a pound to over ten shillings ; but it will be 
found that, by tinting the shade with basic colours of a 
yellower or bluer shade, any given shade can usually be 
obtained from any one eosine, whether it be a cheap or 
an expensive* brand. Of the cheaper brands, Eosine A 
(B.A.S.F.) and Eosine GBF of Cassella are about the most 
satisfactory and reliable. 

From the most easily manufactured and most fugitive 
lakes, it is now necessary to pass to the consideration of 
the most difficult lakes there are to manufacture, and the 
most permanent when properly made of all lake pigments, 
namely, the oxyketone colours, i.e., the alizarines, and allied 
ortho-dihydroxy colours, whether they contain other lake- 
forming groups or not. The remarks concerning these 
colours apply also to such colours as Gallein, Ccerulein, 
etc., which, however, produce violet and green lakes. 

Many and various recipes for the manufacture of these 
lakes are given, some of which yield lakes suitable for one 
purpose and unsuitable for another. It is not intended to 
go into the details of these methods, but to give an outline 



96 THE MANUFACTURE OF LAKE PIGMENTS. 

of the most essential points to be observed in manufac- 
ture, which are applicable to the production of lakes from 
these colours by nearly all the method^. 

The lake-forming bodies for these colouring-matters are 
the oxides of aluminium, iron, and chromium. These 
bodies alone do not yield lakes of great fastness or brilli- 
ancy, unless they are combined with calcium oxide, form- 
ing a double aluminium, iron, or chromium, and calcium 
salt. To obtain the brightest and most permanent alu- 
minium lake, oleic acid or a similar body must be present. 
The exact composition of the lake cannot be accurately 
stated. The reds derived from the alizarine colours are 
among the most important of all lake colours and the most 
difficult to manufacture ; as in dyeing, the brightest reds 
from these dyestuffs are those in the aluminium mordant, 
the brightest lakes are those in the aluminium base. 

A study of the careful way in which cotton is mor- 
danted for alizarine reds is of help in attacking this prob- 
lem. It is one in which there is no royal road to success, 
for there is not the slightest doubt about the fact that what 
works well in the hands of one manufacturer is of no use 
in the hands of another, some slight unnoticed deviation 
causing the resulting product to be inferior to the exact 
article required, and it is only by careful study in the colour 
laboratory and then by careful attention to details in the 
colour-house that a constant and reliable product can be 
obtained. 

In the first place the presence of even minute traces of 
iron in any one of the chemicals or materials used is quite 
sufficient to destroy the brightness and brilliancy of the 
lake, turning it dull and causing it to reduce to a dirty pink 
instead of almost as bright a reduction as that given by 
eosine. The presence of undeveloped dyestuff is also a great 



RED LAKES. 97 

bugbear. To avoid this there is only one safeguard, that 
is, to proceed very slowly in all stages of the manufacture. 

The problem the lake manufacturer is set is not only 
to obtain a given shade or a given strength, but also to 
obtain a lake having the same physical characteristics as 
the sample, such as opacity, hardness, or softness, and 
similar working properties in oil and ink. With such a 
complex base as that of the alizarine lakes it is very easy 
to make a slight mistake, spoiling the whole of the resultant 
lake. 

Where possible, until the lake is fully formed, it is 
advisable to use distilled water for all solutions. The 
aluminium sulphate should be very carefully tested for iron, 
and, if it cannot be obtained sufficiently pure for the pur- 
pose, potash alum should be used. There is considerable 
difference in the lake produced from potash alum and 
aluminium sulphate. It has been found impossible by the 
author to match an alizarine produced by potash alum by 
one produced by aluminium sulphate. Very close approxi- 
mations were obtained, but they were much harder and 
more granular. 

To eliminate the introduction of chlorides or acetates 
it has been found advantageous to precipitate the amount 
of calcium salt needed as phosphate, washing well and then 
taking same up in the solution of aluminium salt to be used 
to produce the lake with the addition, if necessary, of a little 
phosphoric acid. 

Nearly every maker of alizarines gives one or more 
methods for making these lakes, all more or less useful. 
Each and all have to be modified and adapted to the par- 
ticular lake the manufacturer has in view. 

The most satisfactory lakes are made on the following 

basis : The alizarine is dissolved in a dilute solution of 

7 



98 THE MANUFACTURE OF LAKE PIGMENTS. 

sodium carbonate and sodium phosphate, the solutions 
being kept very dilute ; alizarine oil, i.e., sulphated olive 
oil, is then added, and the mixture agitated for several 
hours, during which a dilute solution of aluminium sul- 
phate or alum is run in very slowly, the evolution of carbon 
dioxide never being allowed to become vigorous. After 
the addition of the whole of the aluminium sulphate, 
calcium acetate is added, also in ver} 7 dilute solution ; the 
mixture is left for a couple of days, being, however, oc- 
casionally stirred ; heat is then applied and the whole 
mixture raised to the boil very slowly in about four hours, 
and boiled for about an hour and a half. 

The formation of the aluminium alizarate may be as- 
sumed to take place at once ; but the precipitation of the 
lake does not take place until heat is applied ; and the 
decomposition of basic aluminium sulphate, formed on 
addition of dilute aluminium sulphate to the dilute alkaline 
solution, permits, during the time allowed, the formation 
of the complex calcium and aluminium base, with which 
alizarine yields its brightest shades. 

Another method which is fairly satisfactory is to pre- 
cipitate the aluminium hydrate first by means of sodium 
carbonate ; wash quite free from all salts, then add the lime, 
phosphate, and turkey-red oil, and finally the alizarine in a 
thin cream, and boil for several hours. This method avoids 
the great frothing which always occurs with the first method 
and permits of smaller vessels being used. 

Heating the lake in an autoclave instead of boiling is 
recommended. Better results, however, are obtained if 
the batch be first boiled, allowed to settle, the supernatant 
liquid decanted off, and the precipitate finished in an auto- 
clave at about 60 lb. pressure for an hour, then thoroughly 
washed before drying. 



BED LAKES. 99 

The presence of compounds of phosphoric acid plays a 
very important part, for not only does it prevent the horny 
hardness of dry aluminium hydrate giving undesirable 
propert.es to the finished product, but, as we have seen in 
dealing with basic colours of the amido class, phosphoric 
acid compounds possess lake-forming properties when com- 
bined with aluminium. Alizarines being basic colourina- 
matters of the hydroxy class act also as one of the lake- 
forming constituents of the pigment. 

When iron or chromium is used, the same method 
should be adopted, using a salt of the metal of which the 
lake is required, instead of a salt of aluminium. 

These lakes for paper-work rather lack body, but are 
used for tinting purposes, yielding, when reduced, shades 
very similar to those produced by eosine, not quite so 
bright, but infinitely faster. When badly made, they are 
very much duller, and this has caused many stainers to 
look with suspicion on alizarine lakes. 



CHAPTER IX. 

ORANGE, YELLOW, GREEN, BLUE, VIOLET, AND BLACK 
LAKES. 

The methods adopted to produce lakes of other colours 
than red are substantially the same as those described in 
the preceding chapter, attention being paid to the consti- 
tution of the colour, whether it be acid or basic, and the 
process for converting it into a lake pigment devised 
accordingly. 

Orange lakes are principally manufactured from azo- 
sulphonic acids, since these yield much fuller and brighter 
colours than the basic oranges, such as the Phosphines. In 
conjunction with orange lakes, it is as well to note here that 
there are several of the azo-pigment colours giving various 
shades of orange, e.g., Fast Orange Paste of By, which 
merit consideration, but they are dealt with in the dis- 
cussion of the other colouring-matters of that class. 

Nitro-alizarine, or Alizarine Orange, is not used in the 
production of lake pigments, since the presence of the nitro 
group interferes with the ordinary methods used in the 
production of alizarine lakes. 

There are a large number of orange dyestuffs in the 
market belonging to the azo group ; they are mostly 
hydroxy-sulphonic acids, and, in the selection of orange 
dyestuffs, the same rules should be followed as those men- 
tioned in the case of azo-scarlets. 

The precipitating or lake-forming agent is therefore 

(100) 



ORANGE AND BROWN LAKES. 101 

barium chloride, and the base aluminium hydrate, or a 
mixture containing a fairly large proportion of that body. 

Of the various orange dyestuffs in the market, for cheap 
colours the Mandarins B and G (Ber.) give very satisfactory 
results ; for an intermediate quality, Orange II (Basle) 
yields clear bright lakes. The extra qualities of the Brilliant 
Oranges and E (M. L. & B.) yield about the most satis- 
factory results of any of the numerous orange dyestuffs. 

In the production of cheap orange lakes, it is permissible 
to use a much higher percentage of clay in the base than 
with most colours. Orange lakes are largely made by pre- 
cipitating a cheap orange on barytes, to produce imitation 
red lead ; the orange lakes so made, however, are not very 
fast, and soon fade. 

Brown lakes of various shades are principally derived 
from Bismarck brown by the formation of the tartar 
emetic and tannic acid lake in the same manner as similar 
lakes are prepared from basic red colouring-matters, the 
shade being modified by the addition of a red or blue basic 
colouring-matter as occasion demands. 

There are a number of acid browns in the market which 
find considerable use in the manufacture of peculiar shades 
of brown which cannot readily be obtained from Bismarck 
brown and its congeners. They are mostly amido-sulphonic 
acids, and cannot be readily formed into good lakes by 
barium chloride, but must be also combined with tannic 
acid to produce the best result. In some cases this is not 
done, but a small quantity of a solution of albumin is run 
into the cold preparation and the temperature gradually 
raised to the boil. 

The chromates of lead and zinc have for a long time 
made the production of yellow lakes, save for special pur- 
poses, of little or no interest. But, as in the case of the 



102 THE MANUFACTUEE OF LAKE PIGMENTS. 

pigment oranges and scarlets, the pigment yellows of equal 
fastness and strength to the purely chemical colours above 
mentioned have been introduced. They are of the usual 
azo-pigment type and are discussed under that heading. 

The yellow dyestuffs are principally used to modify 
the shade of green lakes. The two principal basic yellow 
colours are Auramine, a diphenyl-methane colour, and 
Thioflavine T, a thiophenyl colour. There are numerous 
acid yellows, of which Naphthol Yellow S, Metanil Yellow, 
Quinoline Yellow, and Tartrazine, a hydrazine xylene yellow 
(of Sandoz) colour, are the most useful for lake production. 
Naphthol Yellow S gives a lake very fast to light but 
which is soluble in water to a considerable extent and 
can readily be detected when present in a lake by the 
solution it gives with hot water. Metanil Yellow has the 
same fault but to a lesser degree. Tartrazine gives deeper 
shades which, however, are fairly fast to light. Quinoline 
Yellow and Xylene Yellow give good lakes of a very pure 
tone, the Xylene Yellow producing if anything the better 
pigment. 

Auramine gives a very good lake on blanc-fixe, suitable 
for use in surface paper- work in place of lemon chrome, 
where it is essential that the colouring-matter used should 
be lead-free. Care must be taken in manufacturing this 
lake not to boil it, or the colour, at any part of the process, 
or the shade will be much deteriorated. 

The two basic yellows, Auramine and Thioflavine T, are 
both used in the production of greens from purely basic 
dyestuffs, the Auramine giving a myrtle shade, the Thio- 
flavine T the purer shade, but the latter is much the 
more expensive. 

A common method for the production of cheap green 
lakes is to add a basic green colour to an acid yellow and 



YELLOW AND GREEN LAKES. 103 

precipitate the two with barium chloride. This method 
cannot be too strongly deprecated, since it yields only 
fugitive shades, which, on drying or standing in the pulp 
state, after washing, dissociate giving the lake a mottled 
yellow appearance. 

Naphthol Green S gives pigments which, though dull, 
are of the fastest to light and exposure generally produced. 

Where purely basic greens are used, or where the 
pigment is formed by methods used for the precipitation 
of basic colours only, the basic yellows, Auramine or Thio- 
flavine T (C), should be used. The shade of the yellow 
used influences the shade of green produced. 

With acid colours, Naphthol Yellow S is largely used 
for the production of pure shades of green ; but when the 
yellow predominates in light shades, Quinoline Yellow and 
Xylene Yellow are to be preferred, since these give more 
delicate tints. Metanil yellow works well with greens 
used to produce the double barium and tannic acid lakes, 
since it contains an amido group ; it yields sage-green tones 
of a peculiar cast. 

Green Lakes. — Green colouring-matters occur in the 
triphenyl-methane group for the most part, and are either 
purely basic colours or sulphonated amido colours, the acid 
properties of which overcome the strong basicity of the 
numerous amido groups, but from which lakes can only be 
formed when both the amido and the sulphonic-acid groups 
have entered into combination. 

From purely basic colours, such as Ethyl Green, 
Diamond Green, etc., the arsenious acid precipitation 
method gives by far the most brilliant results, the tartar 
emetic and tannic-acid lakes on any base appearing dull 
and insipid beside them. 

When acid green colouring-matters are used, it will 



104 THE MANUFACTURE OF LAKE PIGMENTS. 

often be found that barium chloride will give a fairly satis- 
factory green lake, more especially when an acid yellow 
colouring-matter is used to tint the colour ; but it should 
on no account be forgotten that to produce the fastest as 
well as the most brilliant lake the amido groups which all 
these acid greens contain should be also combined with 
tannic acid and tartar emetic. 

There is very little to choose between the brands of 
the various purely basic greens in the market. Preference, 
if any, might be given to the Ethyl-green crystals (Ber.), 
the Brilliant Green of (C), and the Diamond Greens of 
B.A.S.F. Of the acid greens, of the many that the author 
has examined, the Acid Green D (Cone.) of M. L. & B. gives 
the most satisfactory results as regards both fastness to 
light and brilliancy of shade. 

Coeruleine gives extremely fast shades of green, which 
are not made much commercially, since the process that 
must be adopted is similar to that used in the production 
of lakes from alizarine and allied colours. 

Great use is made of the fact that many of the basic 
greens, especially Malachite Greens, combine with green 
earth directly, giving very fast shades to light, alkalies, and 
bleeding, and as the preparation of the green earth is 
improving, so are the pigments derived from them in the 
properties mentioned. It must be remembered in the 
production of this class of pigment, that the quality and 
properties of the green earth are of as much if not more 
importance than the colour or colours used. 

Blue lakes for certain shades are largely used, but since 
they are derived from basic or sulphonated basic colours, 
they are rather fugitive, and mineral pigments, such as 
the ultramarines and the ferrocyanide compounds of iron, 
are preferred to them. 



GREEN AND BLUE LAKES. 105 

The colours from which they are derived belong chiefly 
to the triphenyl-methane group, the Oxazines, Thiazines, 
and Azines, and the purely acid blues of the azo group 
derived from benzidine. 

With the basic colours the most satisfactory lakes are 

produced by tannic acid and tartar emetic, which yield 

full deep blues of rather a reddish tone. The purely basic 

blues of the triphenyl-methane group can be typically 

represented by — 

/C H 4 N(C,H 5 ), 
Nile Blue, C— C 6 H 4 N(a,H 5 ), 

\c i; h 4 n(c:h 7 )hci, 



/C H 4 N(CH 3 ) 2 
and Victoria Blue, C— C 6 H 4 N(CH 3 )., 

\C 6 H 4 N(C 6 H 5 )HC1 



The oxazines and thiazines by- 



Naphthalene-Blue R (By.), C1(CH 3 ) 2 NC c H./q ">C 10 H 6 

| I 

Nile Blue A (By.), C1(CH 3 ) 2 NC 6 H /^C 10 H 5 NH 2 



Methylene-BlueB(B.A.S.F.),Cl(CH 3 ) 2 NC B H 8 <^g\c 6 H 3 N(CH 8 ) 2 
The Indulines by — 

Neutral Blue (C), (CH 3 ),NC,H 3 < | >C 10 H G 

\ N / 



CI C G H, 



With tartar emetic and tannic acid on clay or blanc- 
fixe, these colours yield full deep fine shades of blue of a 
pleasing tone, but they all more or less tend to the red 



10(5 



THE MANUFACTURE OF LAKE FIGMENTS. 



side. To obtain pure blue shades, it is necessary to use 
the acid blues, i.e., the sulphonated basic blues, which be- 
long mainly to the triphenyl-methane colours, and are well 
represented by — 

/C,H 4 NH-C t .H 4 S0 3 Na 
Diphenylamine Blue, C— C H 4 NHC,H 4 SO 3 Na 
\G 6 H 4 NC 6 H 4 S0 3 Na 



/C,;e 4 NH-C H, 
Alkali Blue D (Ber.), C— C,.H 4 NH-C r H r 

\C t; H 4 N-C H 4 Sb 3 Na 



X C H 4 N(CH 3 ) 2 
Patent Blue BN (C), HO— C— C 6 H 2 0h/|°^Cs 

\C H 4 N(CH 3 ) 2 

The Erioglaucine Blues of Geigy, derivatives of — 



H,C„ 



H 2 C 



N, 



H 4 C 6 

I 
NH 4 3 S 

and Xylene Blue of Sandoz. 







so 2 



CJEL 



CH, 



C H 4 
S0 3 NH 4 



The first two are rather difficult to precipitate. In the 
case of Patent Blue BN a satisfactory precipitate is not 
obtained unless, as well as tartar emetic and tannic acid, 
barium hydrate is used to combine with the hydroxy group. 
In the case of Erioglaucines a little hydrate of zinc must be 
present in the base as well as aluminium hydrate, otherwise 
complete precipitation is not attained. The shade produced 



BLUE LAKES. 107 

from Erioglaucine A is a very pure azure blue, as also is the 
shade produced by Xylene Blue of the Sandoz Co., Basle, 
which has also the further advantage of being much more 
easily precipitated. 

The production of a blue lake with a very high bronze 
and high staining power for lithographic work is made by 
combining together two such colours as Alkali Blue and 
Victoria Blue, and forming the lead salts of the sulphonic 
acids present by precipitating the combined colours with 
lead acetate. 

The process is carried out in the following manner: 
10 lb. of alkali blue are dissolved in about 200 galls, of 
water at the boil, H lb. of 168° T. sulphuric acid added, 
then 5 lb. of Victoria Blue separately dissolved in 150 galls. 
of water run in, and finally 3 lb. of acetate of lead added 
in about 10 galls, of water ; the mixture allowed to stand 
for thirty-six hours to cool and settle, the supernatant 
liquid run off, and the lake filtered off and dried at about 
60° C. The essential point to be remembered is that 
the solutions, in all cases, must be very dilute. Washing 
is not necessary because of the small amount of materials 
used and the dilute nature of the solutions. 

There is very little to choose between the brands of 
blue or the groups in which they occur. The acid blues 
of the azo group are not much used in the production of 
lakes, since equally fast and more brilliant blues can be 
produced from the basic blues and acid blues of the other 
groups, at a much less cost. 

The deep blues that might be obtained from the alizar- 
ine blues have, in the form of lakes, little or no market, and 
are therefore not manufactured. 

Violet lakes are produced mainly from basic violet 
colours which belong to the same groups of colours as the 



108 THE MANUFACTURE OF LAKE PIGMENTS. 

blues just described. Where acid violets are used, the 
ainido groups must be combined with tartar emetic and 
tannic acid, and the sulphonic acid converted into the 
barium salt, if the full beauty of the colour is to be de- 
veloped. 

Purely basic violets give the brightest results when 
precipitated with phosphoric acid. The tartar emetic and 
tannic acid lakes are usually bluer in tone, but duller. 
They are, however, slightly faster than the lakes obtained 
by the phosphoric acid precipitation. The violets are often 
tinted with redder basic colours to obtain the desired 
shade. In all cases where softness of tone is desired, 
Ehodamine should be used, since Magenta or Safranine 
gives rather harsh shades. 

The fastest violet lakes are produced from gallein in 
the same manner as the alizarine lakes. The shade is 
much duller than the violets produced from the basic and 
acid violets, but much faster. 

Black lakes are mainly produced from the azo-acid 
colours. They are treated in the same manner as the 
azo-scarlets ; since the shade they give in lakes is rarely 
ever a full deep black, but is of a bluish cast, they are often 
thrown down on a base containing a carbon black in the 
form of lamp, vegetable, or ivory black, the shade of which 
they modify. The pure lakes, however, are largely used 
for tinting purposes ; but the lakes produced from logwood 
are much cheaper than those from the artificial colours, 
w r hich consequently are not in much demand. The di- 
amino blacks, the black F.H.A. of Basle, and others give 
shades of black ranging from a bluish to a reddish shade. 
The indulines are largely used in the production of inks 
and stencil black, but very rarely as lakes — usualty as the 
spirit soluble varieties. 



Manufacture of Lake Pigments 



To face page 108 



VIOLET AND BLACK LAKES. 



109 



Plate VI. shows some shades produced by both basic 
and acid dyestuffs ranging from reddish-yellow to black. 



No. 1 shows Afghan Yellow E 



(Brit. Dyes). 



No. 2 , 


, Bismarck Brown Tannin Lake ,, , 


No. 3 , 


, Alkali Blue 2B , 


No. 4 , 


, Soluble Blue 3M 


No. 5 , 


, Fast Acid Black H „ 


No. 6 , 


, Naphthalene Black B „ , 



CHAPTER X. 

THE PRODUCTION OF INSOLUBLE AZO COLOURS IN THE 
FORM OF PIGMENTS. 

The introduction of Primuline and of the method of dye- 
ing ingrain colours by Green in 1887, by which the amido 
groups of the Primuline were diazotized after dyeing on 
the fibre and then combined with an amine or a phenol, 
led to the introduction of a large number of colours 
capable of being treated in this manner, together with the 
process of impregnating cotton with a solution of a phenol 
and producing an insoluble azo colour by passing it through 
a solution of a diazotized compound. 

Of recent years, owing mainly to the general fastness 
of the colours so produced, this process has been applied 
to the production of pigments by the formation of insoluble 
azo colours on suitable media, more especially those of 
a red colour. These products cannot be regarded in any 
way, however, as lakes, but rather as strong pigments 
diluted in the process of formation by suitable substances, 
to make them of service as paints and colours for allied 
work. 

Very few dyes are used for this purpose, for, apart from 
primuline, the colours produced from dyes are browns, 
blues, and blacks, which colours produced from coal-tar 
products are but little in demand ; and the red shade pro- 
duced from diazotized primuline and /?-naphthol is very 
little superior to that produced more easily from an ordin- 
ary azo-sulphonic acid. 

(110) 



THE PRODUCTION OF INSOLUBLE AZO COLOURS. Ill 

These pigments are therefore produced almost entirely 
by diazotizing an amine and then combining it with a 
phenol or amine in solution, in which is suspended the 
base or bases which it is desired to colour. 

There are several methods in use, the principal being 
the simultaneous production of* the azo colour and the 
resinate or phosphate of zinc or aluminium, by adding to 
mixed solutions of a phenol or amine and the sodium salts 
of either resinic or phosphoric acid, a diazo solution con- 
taining salts of either aluminium or zinc. Meister Lucius 
& Brunning strongly recommend the use of resinate of 
soda ; but pigments containing resinates do not work at 
all well in oil, and, for pulp colours, though very bright, 
they are apt to work thin and transparent. 

With the azophor reds of the above-mentioned firm, 
pigments of fair brilliancy and of soft easy-working tex- 
ture have been obtained, by using sodium sulphate along 
with the solution of the naphthol, and barium chloride 
with the diazo solution. 

Previous to the closing of the main continental source 
of the artificial colouring-matters, there was available a 
long range of shades, from a pale lemon of the Pigment 
Yellows to the almost crimson of Permanent Red 3B. 

They were divisible into two classes, those which were 
a combination of amines and naphthols, and those which 
contained a sulphonic-acid group. The former were used 
simply as pigments of high staining power, and ground 
into the base either in the dry or in pulp, being afterwards 
dried and ground, or otherwise prepared for market. 
The sulphonic acids were for the most part very slightly 
soluble salts, and were sold usually as stiff pastes contain- 
ing 20 per cent, of colouring-matter, but sometimes as the 
dry powder. The shade was developed and modified by 



112 THE MANUFACTURE OF LAKE PIGMENTS. 

substituting the sodium in the sulphonate by barium, 
calcium, zinc, or lead, each of which modified the shade 
somewhat, giving it a bluer or a yellower cast as the case 
might be ; barium and zinc gave the yellower tones, lead 
and calcium the bluer ones. In some of the deeper shades, 
manganese sulphate gives the best shades of all. 

The fastness to light of these colouring-matters varies 
from poor in the case of Paranitraniline Red, to medium 
in the case of Lithol Reds and fairly good in that of Helio 
Fast Red RL. Some are more soluble in benzol than 
others. All those that are not salts of the sulphonic acids 
are soluble in hot benzol. The sulphonic acid salts are not 
soluble, and this gives a ready method of testing which 
class of these colours is being dealt with. They also vary 
in their solubility in various media, such as linseed oil, 
turpentine, white spirit, and alcohol, so that they are 
prone to bleed when light colours in these media are 
painted over them. In such cases it is advisable to paint 
them over with several different mixtures containing a 
white or very light pigment, before guaranteeing them fast 
to bleeding. 

The manufacture of these colours is very simple, yet it 
should be carried out with care if the best results are to 
be obtained. 

In grinding the colouring-matter into a dry base, 
such as barytes or blanc-fixe, it is better to incorporate 
thoroughly only a portion of the base with the whole of 
the colouring-niatter, adding the remainder of the base 
little by little. 

A little mineral oil is often used to bring up the colour. 
Above 2 per cent, of the total weight of the charge, this 
is not advisable. A much smaller quantit} 7 than this can 
be used if the oil be dissolved in a little benzol before use. 



THE PRODUCTION OF [NSOLUBLB A.ZO COLOURS. 113 

The latter is fairly volatile and volatilizes during the 
grinding, leaving the heavier oil very much more evenly 
distributed throughout the whole mass, and, since many of 
the azo colours, as has already been stated, are soluble in 
benzene, this reagent, by partial solution, helps to bring up 
the shade more rapidly. Great care must be exercised 
both in respect to the quantity used and the proximity of 
naked lights, since the vapour of benzene is highly in- 
flammable. 

Where pulp azo colouring-matters are used, it is 
advisable to incorporate thoroughly the pulp colouring- 
matter with the base, and afterwards to drive off the ex- 
cess of water before grinding and finishing in the ordinary 
way. 

With paste and dry colouring-matters of this class, 
which require the addition of barium or calcium salts to 
develop the shade, it is by far the best method to break 
down the required quantity of the pulp into a thin cream 
with water, sieve into a suitable tank or vat through a 20- 
mesh sieve, raise if necessary nearly to boiling, run in the 
base with more water through a sieve of similar mesh, 
stirring the whole time, and then to add the requisite 
quantity of the barium or other salt. If the shade requires 
boiling — necessary in some cases to produce an alteration 
or a further development — boil for the required time. 
Finally, fill up with cold water, allow to settle, and wash 
by decantation once or twice according to the amount of 
pigment present. 

Adding the barium or other salt to a thick mixture in 
a pan mill, or working with too thick mixtures of the 
colouring-matter and base, may increase output and the 
speed with which the work can be done, but the product 
is much inferior in quality, and is nearly always but 



114 THE MANUFACTURE OF LAKE PIGMENTS. 

partially developed, giving rise to faults and complaints 
as to the constancy of shade and the reliability of the pig- 
ment. 

The combinations of the diazotized amines with the 
various phenols and amines, to produce these colouring- 
matters, are mostly patented. In the transient stage of 
the dye-making industry in this country it is to be recom- 
mended to the pigment manufacturers that they obtain 
a licence to use these methods, and prepare their own 
colouring-matters from the intermediate products. They 
will not be able, at first, to produce so fine a quality of 
material as the original makers, nor will their product be 
quite so constant owing to variations in the intermediate 
products, but the pigment manufacturers will be able to 
satisfy their own requirements, and to relieve the pressure 
on the British dyestuft' manufacturing firms until these 
are in a position to cater for their requirements more 
cheaply than they can make the required substances them- 
selves. 

A careful study of the reactions and the chemical nature 
of the various phenols and amines used will show that, 
if the physical requirements of the production of these 
colouring-matters be carefully attended to, little difficulty 
will be experienced in manufacturing them. 

Plate VII. — The behaviour of these colouring-matters is shown 
in Plate VII, which shows Lake Red P of British D\ 

I. On Barytes. 
II. ,. Blanc-Fixe. 

III. .. China Clay. 

IV. ,, Barytes and Alumina. 

V. .. Blanc-Fixe and Alumina. 
VI. .. Clay and Alumina. 




Manufacture of Lake Pigmenth 



To face page 114 



THE PRODUCTION OF INSOLUBLE AZO COLOURS. 115 

The reactions involved are well illustrated in the pro- 
duction of the best known of these colours, viz., Para- 
nitraniline Red, which is produced by combining diazotized 
paranitraniline withJ/3-naphthol. 

Paranitraniline C (1 H 4 \ ,^tj is a bright yellow powder 

of a crystalline nature, which is very slightly soluble in 
water, but soluble in hydrochloric acid, producing the 
hydrochloride. This salt is fairly soluble in boiling water, 
but unless the solution be very dilute it is reprecipitated 
on cooling ; 1 to 2 per cent, solutions only do not deposit 
on standing. The aqueous solution of the hydrochloride 
has a clear yellow colour, which tarns slightly browner 
when the nitrite of soda is added, owing to the amido 
group being converted into the diazo group. Thus — 

U « M 4 NH 2 H C1 + HNOo " U ^N : N . CI + 2H,0 

The paranitro-azo chloride is very unstable, readily 
decomposing above 50° F. with the evolution of nitrogen, 
which together with the deepening of the colour indicates 
that for the purpose of pigment-making the preparation 
is wasted. A slight deposition of the hydrochloride in 
the original paranitraniline solution, before the addition 
of sodium nitrite, may be ignored ; but, unless, before de- 
composition sets in, the insoluble matter has entirely dis- 
appeared, it is useless to proceed, since specks of yellow 
will pervade the resulting pigment, and the colour pro- 
duced will be dull and unsatisfactory. 

The diazotized base, when run into a phenol or an 
amine solution, readily combines with it, producing a 
stable coloured compound. Thus — 

r ur N0 * r ft N0 « 

* ■■■' **N :"NC1 + C ]0 H 7 ONa _ ^^^ : NC^OH + NaCl 



lit', THE MANUFACTDBB OF LAKE PIGMENTS. 

Various makers of paranitraniline give recipes for the 
preparation of these pigments, nearly all of which produce 
excellent results if carefully carried out with pure chemi- 
cals ; but, commercially, where the materials used at one 
works differ a little from those used at another, adaptation 
of details to existing conditions is essential. It is, there- 
fore, of little value to give minute instructions for the pro- 
duction of these pigments, since considerable practice is 
necessary to obtain really good results. A good plan is to 
work out carefully, with pure chemicals, some recipe such 
as the following, and to apply to it those corrections ren- 
dered necessary by impurities in the ordinary supplies : — 





'224 


parts blanc-fixe 


Co *»\V-i t V» *~»1 


2o 


.. /3C 10 H-OH 


> apnincu i 


0-7 


.. XaHO' 


mixture 


2o 


.. Xa 2 C0 3 




1-0 


„ oleine 



2-4 parts C,H 4 XO.,XH„ 
Diazo | 6-0 .. HC1 1-2 sp. gr. 
mixture "l 1-22 NaNO, 



[20 



250 ,, water 

On examination the reagents in this recipe will be seen 
to be in molecular proportions, and, unless the mixtures 
when added together give an almost neutral or preferably 
slightly acid mother liquor, the resultant pigment will be 
disappointing. In the presence of an excess of mineral 
acid, the colour, instead of being bright red, is brickish, 
and, with alkali, dull and dirty. The presence of a little 
acetate of soda in the naphthol mixture is advisable, since 
the presence of acetic acid has not, even in fairly large 
quantities, the deleterious action of free hydrochloric acid. 

These colours are easily made when attention is 
carefully paid to detail, but the details cannot be given, 
since they differ under various conditions, and are only 



PLATE VI 11 





















■■■ 




HUH 





Manufacture of Lake Pigments 



To face page l W< 



THE PRODUCTION OF INSOLUBLE AZ<> COLOURS. 117 

to be learnt by careful experiment and close attention to 
the chemistry and behaviour of the materials used, and 
of the intermediate products formed in the course of 
the operation. 

The following are some of the principal naphthols and 
amines used to combine with the various diazotized bases : — 

/?-naphthol. Phenol. 

a-naphthol. /3-naphthol disulphonic acid. 

Diphenylamine. m.-phenylene diamine. 

Eesorcinol. a-naphthol sulphonic acid. 

They are often sold under the name of developers, and 
are then usually prepared for use by combination with 
sodium in the case of phenols, and with acids to form salts 
in that of the amines. 

Among the chief bases that are diazotized are — 
m. and p.-nitraniline. 
p.-phenilidine sulphate, 
o.-nitro-p.-phenilidine. 
The various azophor reds, etc. 

Plate VIII. — The influence on the shade caused by the base, 
and the influence of the base on the reduction on these 
pigment colours is shown in Plate VIII which shows : — 
I. Lake Red P on Barytes. 

II. Lake Red P on Barytes reduced 1 : 20 with white. 
III. Lake Red P on Blanc-Fixe. 
1 V. Lake Red P on Blanc-Fixe, but reduced 1 : 20 with white. 
Y. Lake Red P on Orange Lead. 

Lake Red P on Orange Lead but reduced 1 : 20 with white. 



CHAPTEK XL 

THE GENERAL PROPERTIES OF LAKES PRODUCED FROM 
ARTIFICIAL COLOURS. 

The physical properties of lake pigments depend on their 
two main constituents — the lake itself, and the base on 
which it is struck or with which it is combined. 

The nature of the base, whether it be in a fine state of 
division or in coarse particles, e.g., blanc-fixe and barytes, 
alters very considerably the appearance of the lake. It 
may be taken, however, as an axiom, that the coarser the 
base the fuller and richer is the appearance of a lake struck 
on it ; the finer the particles of the base are, the paler 
and duller will the product appear. This difference is the 
more noticeable in dry pigments and in those used as 
water colours. With pigments in oil, or in preparations 
containing oil, it is still very distinct but not quite so 
marked. 

The covering power of a pigment is nearly always 
dependent on the base. In alizarine lakes, with arsenious 
and phosphoric acid compounds as bases, the pigments, 
are nearly transparent in oil. Most of the pure lakes them- 
selves possess little or no covering power, and very little 
opacity. The nature, however, of the precipitated lake 
exerts a marked influence on this property. Lakes that 
come down as flocculent precipitates usually have very little 
influence on the body of the pigment, those that come 

down as amorphous powders greatly increase it. Those 

(118) 



PROPERTIES OF LAKES PROW ARTIFICIAL COLOURS. 119 

pigments in which the base is precipitated or partially 
precipitated with the lake usually possess greater covering 
power and opacity than those merely struck on an inert 
base. 

It will be found, more particularly in the case of the 
azo sulphonic-acid colours, that the amount of lake cannot 
be increased with advantage beyond a certain percentage, 
because the lake when dry becomes so hard and horny that 
the full value of its colouring power cannot be made use 
of, and it will not work up as a paint or ink in oil or varnish. 
However, in the case of the simple azo pigment Helio Fast 
Ked RL, the pure pigment itself is very readily worked 
up as a paint, and can therefore be used in all percentages 
in the production of pigments from various bases. 

It cannot be assumed that the covering power, density, 
opacity, and staining power are dependent solely on the 
base, and almost every lake requires consideration and 
modification to produce the best and most economical 
pigment from it. It is only by repeated trials that the 
most suitable base and precipitating agents can be decided 
upon for any individual colour. A pigment well suited for 
linoleum work may be of no value for the preparation of 
lithographic ink. The nature of the precipitate when just 
struck, and when washed and ready for the filter-press, 
the rapidity or otherwise of its filtration, the nature of the 
cakes in the filter-press, whether they be homogeneous 
or hard on the cloth and soft in the middle, often give 
very good indications as to what the finished dry pigment 
will be, and the study of these details frequently enables 
an experienced hand to modify. and adjust some little point, 
thereby correcting a fault which would impair the value 
of the pigment, before it is too late. 

Staining Power. — The same percentage of a colour 



120 THE MANUFACTURE OF LAKE PIGMENTS. 

struck on bartyes and blanc-fixe, say 5 per cent, of an eosine 
precipitated with acetate of lead, will yield colours very 
different in appearance and shade, yet, on reduction in white, 
it will be found that the finer base gives the stronger stain- 
ing lake. This can be accounted for as follows : The 
larger particles of the coarse base are more thickly coated 
with the lake since they expose a much less total surface 
to be covered than the same weight of the finer material : 
in the latter, the colouring-matter is spread over a greater 
surface giving a paler resultant, but one which, on account 
of its greater original extension, can impart a deeper tint 
when reduced. 

In cases where the pure lake has a tendency to dry in 
hard horny masses, care should be taken that too great a 
percentage of the lake be not present in any pigment made 
from it, otherwise, after drying, the pigment will have 
much less staining power than one containing a smaller 
percentage of lake colour. 

In the production of lake pigments for staining, the 
object of the maker is to produce, at the least cost, a pro- 
duct with the maximum staining power. This can only 
be done by careful selection of the base and the amount of 
colouring-matter to be used. 

As a general rule, lakes that are to be used as self-colours 
in paint work are required full and bright of shade in oil. 
The question of their strength on reduction is not one 
of importance. It is wise in this case to use heavy and 
coarse substrata, but where staining power is a desideratum, 
the lighter and finer the base used the better. 

It will be found that lakes made from the alizarine 
dyestuffs and the basic amido colours, such as Bismarck 
Brown and Malachite Green, possess the greatest staining 
power. 



PROPERTIES OF LAKES PROW \ 1,'TI IICIAL COLOURS. 121 

Pigments produced from artificial colouring-matters, 
with the exception of those obtained from alizarine and its 
allies, and from azo colours prepared by combining a dia- 
zotized amine with a naphthol or an amine, are not fast 
on exposure to light, air, and moisture. Their fastness 
varies, but the most fugitive are usually the most brilliant, 
and give the most pleasing shades ; hence they are largely 
in demand. Among the best examples of the most fugitive 
lakes are those obtained from the Eosines, and the tri- 
phenyl methane basic colours, such as Ethyl and Methyl 
Green, Magenta, Nile Blue, etc., which six hours' exposure 
is sufficient to alter to a marked extent. The scarlets and 
greens obtained from the azo colours vary in fastness, 
but are relatively much faster than those previously 
mentioned. The faster colours are those which are 
double and triple lakes, and not merely precipitated 
colouring-matters. Safranines yield fairly fast tannic 
acid' lakes, but they lack brilliancy, otherwise they would 
largely displace the arsenious lakes of Magenta, to the 
shade of which they approximate. 

The media in which the lakes are used greatly affect 
their fastness to light, air, and moisture. When the 
colours are used with size, fading is the most rapid ; in oil 
and lithographic ink the alteration is not so soon evident. 
A lake was made from Orange II, and three strips painted 
on a piece of glass — 

(1) the pulp in size, 

(2) the dried colour, in oil, 

(3) the dried colour in lithographic ink. 

All were exposed to the action of light, air, and moisture. 
After three days 

(1) had faded to a dirty brown, 

(2) and (3) had lost but little brilliancy. 



122 THE MANUFACTURE OF LAKE PIGMENTS. 

Ten days' exposure was necessary to render (*2) and (3) of 
the same shade as (1) after three days' exposure, (3) taking 
slightly the longer time. 

It will be found that a very short exposure to direct 
sunlight, say twelve hours, rapidly deteriorates the bril- 
liancy of the colour, after which the shade changes with 
more or less rapidity ; oranges and yellows become dirty 
and brownish ; scarlets, crimsons, and cardinals darken 
and become much bluer ; magentas, violets, and maroons 
blacken with an entire change in shade ; greens become 
bluer, and bleach with great rapidity. 

In testing the staining or colouring power of a dry 
lake, it is better to use a good linseed oil and white lead, 
but what holds good for a pulp colour will be found to 
hold good with the dry colour. It must be remembered 
that though a lake may be matched to work in size, it 
may not match when worked in other media. In a case 
where an imitation vermilion was required in a great hurry, 
the shade was matched to a nicety with an eosine and an 
orange, when both the sample and the match were tested 
by rubbing out on paper with a little size ; but when they 
came to be tested one against the other in oil, the shade 
given by the eosine-orange match was much too deep and 
red, and the pigment had to be made with entirely differ- 
ent colours. 

There can be no fixed percentage given for dry colour 
in pulp colours since the various classes of lakes vary 
greatly in pulp-forming properties. Care should be taken 
to ensure that, if a lake gives satisfaction, when containing 
a certain percentage of dry pigment, it is always main- 
tained at that percentage, for, if it be sent out containing 
more than the usual percentage, it will not be usable, 
since it will not fall down and work easily in size, and, if 



PROPERTIES OF LAKES FROM ARTIFICIAL COLOURS. 123 

containing a greater proportion of water, it will work far too 
thin. A rough method of testing whether a pulp pigment 
be in proper condition is by stirring gently two ounces of it 
in a vessel with about an ounce of prepared size, by means 
of a stick or glass rod. If the lake has been properly 
made and is in proper condition, it will give, with very 
little agitation, a creamy homogeneous mixture with the 
size. 

Many lakes are partially soluble in boiling water, a 
property of which advantage can be taken when the shade 
of a lake is a little too deep and it is desired to render it 
paler, an operation that cannot be satisfactorily carried 
out by increasing the amount of base present when once the 
lake has been made. Though boiling leads to a little loss, 
such loss is preferable to the risk of spoiling the whole 
product by additions which would demonstrate their 
presence in the finished pigment. The addition of soda, 
oil, or soap to increase the solubility of the lake cannot be 
too strongly condemned, since the beauty of the pigment 
is nearly always destroyed. 

Some pigments being soluble to a slight extent in hot 
water, when struck at or near the boil a considerable 
amount of the lake is dissolved. It is advisable in such 
cases, before syphoning off the supernatant liquor, to allow 
the whole to become quite cold. With occasional stirring, 
practically all the lake is obtained in the pigment, and, in 
addition, a considerable increase in brightness of the fin- 
ished product results. 

The solubility of a lake in water has certain draw- 
backs, among which is the fact that such a colour cannot 
be completely precipitated. The necessary washing in- 
creases the loss, and, in use, the colour bleeds, rendering 
it unfit for use for many purposes. 



124 THE MANUFACTURE OF LAKE PIGMENTS. 

Bleeding, however, can be caused otherwise than by the 
solubility of the lake ; for, in a case that came under the 
author's notice, where a batch of colour had been made 
in a tank that was only fitted for making half the quantity, 
the wash waters came away quite clear, with the result 
that more washing than usual was given ; but, when the 
colour came to be used in size for surface papers, it 
bled so frightfully that it was of no use, yet previous 
batches made in smaller quantities at a time, and de- 
liveries since made correctly have not behaved in this 
manner. 

For pulp colours a pigment should settle, after digestion 
with water for three hours at 50° C, leaving the water 
quite clear, or but very slightly tinged ; dry pigments 
should also be similarly tested in alcohol, glycerine, and 
turpentine. 

The action of heat in some cases causes the shade 
to alter materially. This is very noticeable in those 
maroons made by a combination of Magenta and some 
blue shade of scarlet, more especially where the Magenta 
has not been fixed otherwise than by its property of com- 
bining with the Acid Scarlet ; in some Ponceaux, such 
as Ponceau 4 RB (Berlin), and in greens precipitated by 
arsenious acid with which great care has not been taken. 
As a rule, a good lake can be dried at 100° C. without 
undergoing any change, but, generally, lake pigments 
should be dried in a current of air at a temperature a little 
over 50° C. If they change in drying much below 100° C. 
the conclusions to be drawn are either that the colouring- 
matters have not been properly combined to form true 
pigments, that an inferior grade of dye-stuff is being used, 
that an irrational mixture of one or more incompatible 
colouring-matters has been used, that some error has crept 



PROPERTIES OE LAKES FBOM ARTIFICIAL COLOUBS. 125 

in during the striking, or that the colour has been im- 
properly washed. The use of too concentrated solutions 
of the dyestuff is frequently the cause. Again, an insuffi- 
ciency of the precipitating agent sometimes gives rise to 
this defect. 



CHAPTER XII. 

STRIKING. WASHING, FILTERING, AND FINISHING. 

The correct dyestuff, base, and precipitant may be as- 
sembled, but unless the lake be struck properly the result 
will be unsatisfactory. 

In making or repeating batches of the same lake pig- 
ment, it is very necessary, as far as possible, to strike them 
exactly in the same way and under the same physical 
conditions. The points which need most careful noting 
are : — 

1. To have the solutions always of the same strength, 
and when, after solution, the material is diluted, to dilute 
always to the same extent. 

■2. The temperature at which the lake pigment is 
struck should be noted, and all subsequent batches struck 
at this temperature. The solutions or mixtures that are 
added should be at approximately the same temperature. 

3. The order of addition of the various colouring- 
matters and chemicals should always be the same. 

4. The time taken in making these additions, and the 
rate at which they are prepared, should not vary. 

5. The stirring or agitation of the mixture while in 
process must be exactly the same in all cases. 

Dyestuffs and colouring-matters from reliable firms 

can generally be taken as equal to standard, but, if possible, 

it is advisable to test them. All chemicals, such as 

aluminium sulphate, soda ash, barium chloride, barytes 

(126) 



STRIKING, WASHING, FILTERING, AND FINISHING. I'll 

clay, acids, etc., should be invariably carefully tested to 
ascertain whether they are of the purity and strength re- 
quired for the formula to which the lake is being made. 

It is most unwise to vary any conditions after once 
they have been settled, if succeeding batches of pigment 
are to be identical, for, on the physical conditions under 
which the pigment is made, the physical properties of the 
product depend, and often the slightest deviation from 
these conditions results in variations from the standard, 
rendering the material quite unserviceable. 

Doubling the quantities used when pressed for time 
and large quantities are required, is a foolish policy, for 
the whole conditions of the precipitation are thereby altered, 
and the product cannot be relied upon to be the same as 
one prepared under normal conditions. 

Increasing the time allowed for washing, especially in 
the case of highly aluminous precipitates, is unwise, since 
occluded salts diffuse from aluminium hydrate only with 
difficulty. 

It is not advisable to use too large tanks or vats ; ascer- 
tain the maximum capacity of each striking vessel, and 
work always with that amount. 

Mechanical stirring is to be preferred where heavy 
substrata are used, but, unless this is very easily con- 
trolled, in cases where there is much effervescence at any 
stage of the manufacture, hand stirring should be re- 
sorted to. 

Tanks or vats having a capacity of about 1000 galls, 
are of convenient size for making 4 to 5 cwt. of dry lake 
on a blanc-fixe alumina base, or about | ton of pulp lake. 

However pressing requirements may be, the lake 
manufacturer, having once ascertained by experiment the 
minimum time required and the maximum quantity of 



L28 THE MANUFACTURE OF LAKE PIGMENTS. 

lake he can make with the materials and plant at his dis- 
posal, is only seeking trouble if he varies from these in the 
slightest degree. 

One of the most important operations in the manufac- 
ture of lakes is the washing, or the removal of those soluble 
by-products produced during the various operations. Un- 
less these are entirely removed, it is useless to look for the 
fullest and brightest shades ; and, further, owing to their 
action on the various media used in their application such 
by-products frequently render the pigments of little value. 
It will be found that, in at least 50 per cent, of the cases 
where complaint is made against a delivery of a pigment, 
the cause arises from defective washing. 

The operation of "washing" may be carried out in 
two ways, either by the use of a filtei-pump which niters 
and washes the colour simultaneously, or by decantation. 
The first method is the more rapid, and is extremely effec- 
tive where the pigment is of an open and granular tex- 
ture, e.g., such as imitation red lead, or vermilionettes ; but, 
in colours of a more gelatinous nature, especially high-class 
lakes sold in the pulp form, it is a better plan to wash by 
decantation, since time is required to enable the impurities 
retained in particles of the lake to diffuse into the wash 
water. Experience has shown that, in some cases, where, 
owing to urgency, one part of a batch of colour has been 
washed in a filter-press, it has been rejected, while the other 
part washed by decantation has given every satisfaction. 
The purpose for which the pigment is required determines 
to a great extent the process of washing to be adopted. 
Colours for use in oil, i.e., pigments used by paint grinders, 
linoleum manufacturers, lithographers, etc., can be effect- 
ively washed by the filter-press ; but with high-class lakes, 
more especially those used as pulp colours, and containing 



STRIKING, WASHING, FILTERING, AM) FINISHING. 129 

a high proportion of hydrate of aluminium in the base, it 
is safer to wash by decantation. 

MTosI colours settle completely in about eight to ten 
hours, but the speed of settling is entirely dependent on 
the nature and texture of the lake in hand, heavy base 
lakes settling in much less time than those containing a 
lighter base. It will also be found that many lakes settle 
rapidly and clearly with the first water, but much more 
slowly with each successive washing. This is not due to 
any action of the water on the lake itself, but to. the fact 
that in the saline solution the pigments settle better, and, 
as the soluble matter is eliminated by each successive 
washing, the lake settles with less rapidity. 

When washing by decantation, it has been found to 
be advantageous to arrange that the bulk of the settled 
precipitate is about 25 per cent, of the capacity of the tank 
or vessel in which the colour is made. Three times wash- 
ing in such a case will be found quite sufficient ; for, suppos- 
ing the soluble impurities of a batch to be represented by 
100, the first water taken off removes at least 75 per cent., 
leaving less than 25 per cent, in the tank with the lake, the 
second leaves less than 6*25 per cent., and the third less 
than 1*5625 per cent., fully two-thirds of which is subse- 
quently removed by filtration and pressing. 

In cases of urgency, it is advisable, when the salts, etc., 
in solution have no action on the pigment, to allow as long 
as possible for the first washing since this water contains 
the greater proportion of the impurities it is desired to re- 
move ; and it is better to take off one water after com- 
plete settlement than to remove two or three after partial 
settlement. As a general rule the first water should be 
removed as soon as the pigment has well settled, but, in 

cases where the precipitate being washed is of a gelatinous 

9 



L30 TEE MANUFACTURE OF LAKE PIGMENTS. 

nature, i.e., those containing a high proportion of colour- 
ing-matter or aluminium hydrate, it is advisable to allow 
the second water to remain as long as possible, in order to 
allow the soluble matters entangled in the particles of the 
lake time to diffuse into the wash water. 

When a lake "hangs," as it is termed, in the colour 
house, i.e., does not settle completely with the last water, 
leaving a haze of more or less density, the practice of adding 
a little soda or alum to clear the liquid is to be deprecated, 
since, in- nearly every case, this addition injures the pig- 
ment, and the loss caused by running off the haze together 
with the last water is usually very small. It is wiser to 
suffer this loss than to spoil the lake by tampering with it. 

In cases where the lake refuses to settle with the first 
water, it will be found that there has been some error in 
the manufacture, and whether that error can be corrected 
depends on the nature of the lake and the extent and 
action of the mistake made. 

The filtration of the pigment after washing is completed 
can be carried out in several ways. For dry colours, the 
filter-press is the best method to adopt, since it can be 
regulated to give the pressed and filtered pigment in such 
a state that it requires but little time to dry completely. 

Vacuum filters can be very cheaply and easily fitted up 
in those cases where the outlay involved in putting down 
presses is objected to, the vacuum being produced by an 
ejector or the condensation of steam. The figures on next 
page will illustrate their general construction. 

The method of using either of these forms can readily 
be grasped. The perforated plate C is carefully covered 
and packed, to avoid leakages, with a stout covering of 
calico. The matter to be filtered is poured on until the 
cylinder marked U or U' is about half filled. The taps 



STBIKING, WASHING, FILTERING, AND FINISHING. 131 

T and T' are closed. Where the ejector is used, high- 
pressure steam is admitted to it, when it withdraws the air 
from L', creating a vacuum into which the filtrate rapidly 
runs, a pressure of 15 in. being readily obtainable. The 
steam and valve VN are both shut off at the same time, 
the filter being left until the vacuum is nearly exhausted, 
and the process repeated until the filtering process is com- 
pleted. 




V 



V 



H_=c tP^- S 



l-E 

V 



J N 



A 



V U' 



l-N' 
VN 



FIG I 



FIGE 



Figs. 1 and 2. — A and A', ^ in. iron. B and B', Flanges to support 
C and C. C and C\ J in. perforated iron plates. T and T, Taps 
to run off the filtrate. V V V", £ in. valves. G and G', Vacuum 
gauges. L, Condensation chamber, \ in. iron cylinder with steam 
inlet through V, outlet through B, and connected with A by 
means of iron pipe N, which can be opened or closed by valve V'. 
L', a steam ejector connected with boiler by pipe S, and the air b\ 
outlet H, and with A by the tube N'. 

When the vacuum is produced by the condensation of 
steam, the cylinder E is shut off from the filter A, and the air 
driven out by live steam, through valve V. When nothing 
but steam issues from valve V, the steam is shut off at 
V" and V closed simultaneously, allowing the cylinder to 
cool partially. The connection with A is made by U on 
valve V, which connects the lower portion of A with E. 
The condensation of the steam in E produces a partial 
vacuum, which often indicates as much as 20 in., and the 
filtration proceeds rapidly from U through C into L. 

Both these filters work very rapidly, the only objec- 
tion being that toward the end of the operation the lake 



132 THE MANUFACTURE OF LAKE PIGMENTS. 

frequently stiffens too much at the bottom, giving pulp 
colours rather an uneven and lumpy look ; but in the case 
of dry colours they work very well and economically. 
Neither filter-presses nor vacuum niters, unless the iron is 
well protected from the action of the lake, should be used 
for colours which act on metallic iron, e.g., tannic acid 
lakes, which are blackened and discoloured by such contact. 

For pulp colours of a high class, it is perhaps better to 
proceed slowly by filtering in "open niters," i.e., calico 
spread on wooden frames. This operation requires from a 
couple of days to a week to complete, and, when complete, 
a slight finish is usually given in a hydraulic press. The 
method, though tedious for many lakes, gives a much more 
homogeneous paste which readily breaks down in size. 

Lakes are sold both as pastes and dry. The per- 
centage of moisture varies from 60 to 40 per cent, in pulp 
colours, and great care should be taken to send out any 
given pulp always with the same percentage of moisture. 
Most of these pastes are used with size, and, if the lake 
contain too much water, when it is used, it appears to 
lack body, and is transparent ; if too dry, it thickens the 
size too much, rendering it unusable, since the addition of 
more size would alter the shade and appearance. 

Dry colours are sold in lumps, "drops," and powder. 
When lumps are wanted, it is customary to break the dried 
lake roughly. "Drops " are made by forcing the pressed 
lake, after it has been mixed with a little gum, through 
machines devised for that purpose, the gum being added 
to bind the particles together, so that they will retain the 
form given them by the machine, when dried. Similar 
machines exist for producing lumps of a definite shape, in 
which case also a little gum is added before the product is 
sent to the machine. When a lake has to be powdered, it 



STRIKING, WASHING; FILTEBING, \M> FINISHING. 133 

is not advisable to press it too hard or to dry it too quickly, 
since such treatment diminishes the friability, and renders 
grinding more difficult. 

Where large quantities of barytes have been used, the 
last portions removed from the striking tank frequently 
contain a much greater proportion of barytes than the 
bulk of the product. It is advisable to grind roughly 
the whole batch, distributing this portion throughout the 
whole grinding, before proceeding to grind for the finished 
article. 

The use of a mineral or castor oil for improving the 
appearance of a ground colour is better avoided if possible, 
but, when appearance is a great consideration, it may be 
used, but not to the extent of more than 2 per cent. It 
added in some volatile solvent which volatilizes during 
grinding, the oil is better distributed, and much less oil 
gives the desired effect. More than 2 per cent, of oil has 
a tendency to cause the powdered pigment to cake, but 
it is often used to hide some defect, or to cheapen the 
colour by making insufficient grinding possible. 

Powders must all be carefully sieved before they are 
despatched, otherwise particles not completely ground, 
together with gritty matter, will be found in the pigment, 
deteriorating its quality. 



CHAPTER XIII. 

MATCHING AND TESTING LAKE PIGMENTS. 

The lake manufacturer is asked to match lakes, and, 
often, the only guide given him is a small piece of 
coloured paper or a painted slip. He has then to rely 
more upon his knowledge and experience of the pigments 
than upon any tests he can apply. 

Where possible, a sample of the dry or pulp pigment 
should be obtained. Lakes in oil, varnish, and lithographic- 
ink entail the trouble of removing the vehicle, and, in cases 
where the lake is soluble in the media, it is somewhat diffi- 
cult to isolate the pigment unchanged. 

When a centrifugal machine is not available, the oil 
can usually be readily separated from the pigment by add- 
ing, say, 5 c.c. carbon bisulphide to 15 gms. of the sample, 
stirring well, and diluting up with a mixture of 2 parts 
sulphuric ether and 1 of petroleum ether ; wash by de- 
cantation twice, filter by means of a filter-pump, and 
wash on the filter paper with the mixed ethers until all 
the oil has been removed. 

In cases where the only sample given is but a small 
piece of coloured paper, or dry painted surface, an experi- 
enced lake-maker can usually tell to what class of lakes 
it belongs, and, by referring to his own standards, can 
often devise a lake that will approximately give the colour 
required ; but such a match must always be in a way 

unsatisfactory, for it is almost impossible, where the piece 

(134) 



MATCHING AXD TESTING LAKE PIGMENTS. L35 

of paper has either been rolled, glazed, or varnished, to 
ascertain the actual shade of the untreated pigment. 
Where the sample supplied is a fair one, say an ounce 
or so, an assay of the colour is advisable. This can be 
readily 'carried out under the following scheme:— 

1. Examination of the colouring-matters. 
1 1. Examination of the base. 

Examination of the Colouring-matters. — There are 
many carefully thought-out processes for the identifica- 
tion of the various groups of colouring-matters, notably 
Green's Identification of Dyestuffs, which are of great 
interest scientifically, but take considerable time to apply, 
and this is not always at the disposal of the lake- 
maker. Until experience has been gained it is, however, 
necessary to rely upon these methods, and it is advisable 
starting with those colouring-matters that are frequently 
used in the colour-house, to make and have for personal 
reference standard lakes, and to retain samples of as many 
of the dyestuffs as possible. 

When a colouring-matter has been identified, the con- 
clusion may be verified by reference to a known lake made 
from the supposed colour or by reference to the dyestuff 
itself. 

The examination of the colouring-matter may be carried 
out in the following manner : — 

Take a little of the pigment, rub it out with a little oil, 
put it on a glass plate, and note the shade and undertone. 
In single colour pigments it is often possible, after a little 
experience, to identify the colouring-matter by reference 
to these three points alone. 

Reduce 1 of the pigment with 10 or 20 of zinc white, 
mixing thoroughly, and grinding well on a slate with a 



130 THE MANUFACTURE OF LAKE PIGMENTS. 

muller, or, if only small quantities are being used, with a 
palette-knife on a glass plate 

Nearly all colours, as we have seen, differ in shade. 
The reduction in white accentuates these differences, and 
it ma}' be taken as a safe conclusion that, if a pigment 
gives the same shade in oil and on reduction as one of the 
standard or known pigments, it is probably identical with 
it. The pigment should be treated in the cold with water, 
alcohol, benzene, turpentine, and white spirit, and its solu- 
bility in each of these noted. The mixtures of pigment 
and each of these solvents should then be boiled, and any 
increase or decrease in solubility also noted. 

The sulphonic-acid azo pigments are insoluble, and 
the azo pigments soluble in benzene. This at once gives a 
key to the class should these colouring-matters be present. 
Fastness to Bleeding. — If the pigment be for use as a 
pulp colour, rub out on paper in size ; if as an oil colour, 
paint out on some surface, and allow to dr}\ Paint over 
the dry film a white in size in the case of a pulp, and 
in various media, such as gold size, or some vehicle let 
down with more or less quantities of alcohol, ether, white 
spirit or turpentine in the case of an oil colour, as the 
colouring-matter may be soluble in one or more of these, 
and would then bleed. 

If the pigment does not bleed, then all bleeding colour> 
of that shade are eliminated or rice versa. 

Fastness to light is one of the most important point- 
to determine. It is desirable to expose to sunlight in the 
presence of moisture, but, especially in winter, this cannot 
readily be done in this country, and the exposure cannot 
always be of the same duration. This difficulty can be 
surmounted, when time is important, by exposing painted- 
out films of pigment, in whatever vehicle is to be used. 



MATCHING AND TESTING LAKE PIGMENTS. 137 

to the ultra-violet rays of the mercury lamp, for six hours. 
This, though not equal to the sunlight exposure, gives a 
very good criterion of the fastness to light, an eosine being 
bleached in about two hours and a Helio Fast Bed 
scarcely altered. The rate of fading under these con- 
ditions also gives a good indication of the nature, char- 
acter, and class to which an unknown pigment belongs. 

Several colours give very distinct colorations with 
strong sulphuric acid, and the behaviour of small quan- 
tities of the pigment with this reagent on a white plate, 
especially with reference to known or standard samples, 
is of help in finally determining the colouring-matter used. 

Having noted the shade, the undertone, the strength 
by reduction, the solubility in various solvents, the fastness 
to light, and the behaviour with strong sulphuric acid, the 
following notes on the colour examination may be of use : — 

Take a small portion of the pigment and rub it out 
evenly on a piece of paper with a little size or gum, to 
make it adhere, and dry at about 40° to 50° C. When dry, 
carefully compare the shade with the working standards, 
noting those colours and " makes " which most nearly 
approximate to it. Carefully feel the surface ; if rough, a 
ground mineral base may be expected. Note the fulness, 
density, and brilliancy of the shade, since these properties, 
when considered in conjunction with the results yielded by 
an examination of the base, often suggest the manner in 
which the lake has been produced. 

Cut off a portion of the coloured paper and heat it at 
1G0 C C, noticing whether the shade changes, or if there be 
any alteration in the pigment; for, as previously men- 
tioned, if the colour be a maroon, changing a good deal at 
this temperature, it is to be inferred that the magenta is 
only combined with the acid colour, and therefore a match 



138 THE MANUFACTURE OF LAKE PIGMENTS. 

will have to be so produced as to compete with it in 
price. In other cases, there may be evidence of»some 
weakness, which has caused the user to look for another 
source of supply, and the matcher must then be on his 
guard to avoid this in his own product. 

Divide the remaining piece of the paper, and spot one 
piece with a drop each of a 10 per cent, solution of strong 
nitric and hydrochloric acids. By reference to the valu- 
able tables compiled by various authors, 1 and with the 
help of indications previously obtained by comparison 
with lakes of known composition, determine the group to 
which the colour or colours belong, confirming the decision 
by further tests with the other slips, by spotting them 
respectively with caustic soda or potash, concentrated 
and dilute, and with acetic acid, strong and dilute. 

The difficulty is not so much to identify the colour 
which has been used in the greatest quantity, but to de- 
termine those colours used to modify the shade. 

Roughly classifying the lakes usually presented for 
matching, we shall find that a yellow lake will but rarely 
appear, since the chrome yellows are used, save for very 
special purposes, entirely to the exclusion of the yellow 
lake pigments. A chrome yellow can be so easily identi- 
fied, and is so different from any yellow lake in its behaviour 
with reagents, that it would serve no useful purpose to 
enter into any details of its examination. 

Yellow lakes prepared commercially are usually those of 
Naphthol Yellow S, Aaramine, Thioflavine T, Quinoline 
Y r ellow, and Aletanil Yellow, and examination of the stand- 
ard shade would quickly show from which colour in all 
probability the lake was derived. Of the barium lakes 

1 Georg Zeiss's tables are the most reliable. 



MATCHING AND TESTING LAKE PIGMENTS. 139 

there could be no mistake between those produced from 
Quinoline Yellow, Naphthol Yellow S, and Metanil Yellow, 
and the much greener hue of the Auramine basic lake 
would at once distinguish it from that obtained from 
Thioflavine T. 

The addition of acids would further aid the detection : — 

Naphthol Yellow S — with hydrochloric acid, the colour 
almost disappears, and, with nitric acid, a reddish 
tone appears, which rapidly decolorizes. 

Metanil Yellow — with hydrochloric acid, becomes much 
more red, and, with nitric acid, yields almost a 
scarlet. 

Auramine — with both hydrochloric and nitric acids is 
at once almost decolorized. 

Quinoline Yellow — hydrochloric acid has very little 
action ; with nitric acid becomes more red. 

Thioflavine T is, like Auramine, at once decolorized by 
both hydrochloric and nitric acids, but, unlike aura- 
mine, when treated with caustic soda, becomes 
reddish instead of decolorizing. 

The orange lakes are almost entirely derived from azo 
colours, and the various prices of these afford an indica- 
tion as to which it will be necessary to use, when the 
price of the lake is known. All lake-makers have several 
standards of almost identical shades, but of very different 
prices, according to the nature of the lake pigment required. 
The behaviour of orange lakes with reagents is very 
similar, and the identification of any particular colour 
must, in the main, be determined by the brilliancy of the 
sample, the base with which it is thrown down, and the 
price limit. Frequently the lakes are mixtures of a cheap 
and a more expensive dyestutf, the cheaper colour being 
used to give intensity and fulness, the better one greater 



140 THE MANUFACTUEE OF LAKE FIGMENTS. 

brilliancy and fastness ; and the colour-maker, for his own 
information, should keep a series of orange lakes of as 
great a variety of shades and costs as he can prepare, 
since it is only by such means that he is able to deter- 
mine the constitution of an orange lake put before him. 
It may be advisable to mention here that the lakes made 
from Mandarin R and G, Orange II, and other cheap 
artificial orange colours are much inferior to the more 
expensive colours, such as the Brilliant Oranges of Meister 
Lucius & Brunning. Where time can be allowed, it is 
as well to expose to sunlight for two or three days a 
rubbing of the sample, for in many cases the degree of 
fading indicates fairly accurately the price of the colour 
used in its production. 

Among the red, scarlet, and crimson lakes the question 
of determining the exact colour used in production of a 
given lake is rather more complicated, for it may belong to 
one of five classes, i.e. ; — 

I. Derived from Eosine. 
II. Derived from Alizarine. 

III. A developed azo colour. 

IV. An ordinary lake of a sulphonated azo colour. 

V. A red derived from some basic colour, such as Safranine, 
Magenta, etc. 

An eosine lake is readily recognized after a little 
experience. The peculiar bright bloom and intensity 
of the colour leaves little room for doubt, and very 
short •exposure to light — two or three hours in bright sun- 
shine — will soon confirm such an idea, since the colour, 
if derived from an eosine, will then show signs of fading. 
The identification of a particular eosine is not a matter of 
such great ease, for nearly all eosine lakes are toned by 
the addition of various basic colours to give the required 



MATCHING \M> TESTING LAKE PIGMENTS. 141 

shade, Rhodamines, Safranines, and Rose Bengal being 
those more generally used ; Auramine is also used to give 
a yellow tone, but such a combination is of infrequent 
occurrence. 

Eosines precipitated immediately, however, become 
yellow when treated with acids, and the colour in every 
case is readily dissolved out of the base on treatment with 
an alkali ; even an alkaline salt, such as acetate of sodium, 
has this action, and the addition of a little alcohol generally 
causes the exhibition of considerable fluorescence. 

Alizarine lakes change to yellow much more slowly 
with acids, and do not appear to be affected by dilute 
alkalies; further, their shade and appearance prevent 
them being mistaken for Ponceau lakes. 

The Fast or Permanent Reds show but little change 
when treated with both dilute acids and dilute alkalies. 
This, together with their fastness to light, which is superior 
to that of all but alizarine lakes, gives a ready means of 
identifying them. 

From the great number of Ponceau or Scarlet lakes, it 
is advisable for a lake-pigment maker to select a limited 
number, say nine, with whose properties and chemistry he 
has rendered himself thoroughly conversant, and to use 
these as his scarlets for the production of all lakes derived 
from this source. The use of a separate colour for each 
individual shade causes the number and variety of dyestuffs 
to accumulate rapidly, and it is therefore better to have a 
light medium and blue shade in three qualities of dyes — 
not three qualities of the same dye — and, in various stages 
of adulteration, to secure variety of price and properties. 
The lake-pigment maker will then be able, having once 
determined his standards, readily to match, at a given 
price, any lake pigment derived from this class, by 



14_> THE MANUFACTURE OF LAKE PIGMENTS. 

judicious admixture of the various scarlets at his command. 
If a special case arises, it is a simple matter to go carefully 
into the colouring-matter of such a lake, and to obtain a 
colour with the properties desired, if this is not already 
available. 

Pure Magenta, Khodamine, and Safranine lakes are 
readily identified by their characteristic shades, but are far 
more difficult to recognize when used in mixtures with 
other colours. Magenta is largely used with blue shades 
of Ponceau to produce maroon lakes ; Safranines are also 
used for this purpose, but to a less extent, since their 
greater cost militates against them. Boiling a little of 
the lake with a solution of sodium carbonate, by dissolving 
the magenta or safranine, at once indicates the presence 
of either of these dyes, and, according to the depth and 
colour of the lake, the amount present can usually be 
readily gauged. 

Rhodamines are used with eosine to give blue shades, 
this action on the colour affording a clue to their presence ; 
and, on treatment with acid, a lake containing eosine and 
rhodamine does not become yellow so readily as the pure 
eosine. 

Violet lakes, with the exception of those derived from 
Gallein, which become brown on treatment with acids, 
are for the most part derived from Methyl Violet, acid 
treatment of which changes the colour to blue. The 
shade is modified by the addition of Rhodamines, Magenta, 
etc., the proportion of which, and the colour to use, are 
best determined by comparison with lakes of known com- 
position, since the complications arising from an endeavour 
to isolate the modifying colour in such mixtures makes 
the task one of considerable time and patience. This class 
of lakes is not used to any great extent, so that reference 



MATCHING AND TESTING LAKE PIGMENTS. 143 

to a series of modified violets will usually overcome any 
difficulty. 

A large number of lakes are produced from the various 
basic blues. These lakes, however, differ but little from 
each other save in the redness of tone, and, to produce 
n complete series of shades that can be derived from the 
various basic blues, would be a task of considerable magni- 
tude. It is therefore better to try to discover which 
blue has been used in the production of any particular 
-hade. Those most commonly met with are Nile Blue, 
Methylene Blue, Basle Blue, New Blue, Water Blue, and 
Alkali Blue ; and reference to such a table for the detection 
of artificial colouring-matters as that published by Lehne 
& Kusterholze, appearing in the Journal of the Society of 
( 'In* mica/ Industry, vol. xiv., would quickly indicate the par- 
ticular colouring-matter required to match a given sample. 

The blues derived from allied alizarine colours are not 
met with in commerce to any great extent; those from 
such colours as the Erioglaucines and dyes of similar 
constitution are readily recognized by their pure shade, 
and extremely sensitive reaction to acids and alkalies. 

Brown lakes form an unimportant class, and are mainly 
derived from Bismarck brown modified with other colours, 
the nature of which the shade indicates. The browner and 
deeper shades of maroon are often combinations of Bis- 
marck Brown and a bluish-Ponceau. The Acid Browns 
are used to some extent, but the difference in the lakes 
produced by them is very great, and they are readily recog- 
nized as acid colours. The shade in nearly every instance 
indicates to the experienced lake-maker the brand of colour 
to be used. 

Black lakes, excepting those for tinting purposes, are 
not much in demand, and, usually, one made from some 



144 THE MANUFACTURE OF LAKE PIGMENTS. 

good black colouring-matter will meet requirements. Black 
lakes of a full deep colour are difficult to produce, the ten- 
dency being towards a deep navy-blue. Where a full deep 
black is met with, it is usually either a combination of 
logwood, or contains some black, like lamp, bone, or 
vegetable black. 

The Examination of the Base. — The presence of some 
ground mineral can usually be detected by the " feel " of the 
lake when rubbed out on paper ; but the following plan has 
been used with considerable success to determine roughly 
the constituents of a base. A small quantity of the dried 
lake is introduced into a porcelain crucible, and heated. 
In the case of arsenical colours the fumes of arsenic trioxide 
given off indicate, by their odour of garlic, the presence of 
arsenic. If the residue is almost entirely soluble in dilute 
acid, and aluminium hydrate is precipitated from the solu- 
tion on the addition of ammonium hydrate, it may generally 
be concluded that the lake is an arsenical lake on a base of 
aluminium arsenite ; if a phosphate, the precipitation of 
the phosphoric acid with ammonium molybdate shows the 
phosphate of aluminium to be in all probability present. 

The colouring-matters are usually driven off or burnt 
by incineration in the crucible, the base or bases and 
the precipitating agent remaining. The presence of alu- 
minium, iron, lead, or other inorganic matters can readily 
be detected by ordinary qualitative analysis. AVith a little 
practice, the insoluble residue can be identified without 
complete analysis, since it usually consists of either clay, 
barium sulphate, calcium sulphate, or mixtures of these. 
Calcium sulphate may be detected by adding a solution 
of sodium acetate and acetic acid to the ash : the calcium 
salts are taken up, and, after filtering and adding am- 
monium oxalate, are thrown down, calcium oxalate being 



MATCHING AND TESTING LAKE PIGMENTS. 145 

insoluble in acetic acid. Clay does not settle so readily as 
barium sulphate, but an intimate mixture of clay and 
precipitated barium sulphate is rather difficult to determine 
casually. Washing and drying the residue will enable the 
presence of clay to be determined, since it imparts a 
peculiar shiny appearance to the dried residue. Clay being 
an aluminium silicate, the silica can be driven off by 
treatment with hydrofluoric acid, and extraction with 
water will then leave only the sulphate of barium. 

When ochres or other highly ferruginous compounds 
have been used as part of the base, the colour of the ash 
and the quantity of iron present indicates their use. If 
the quantity be not very excessive, but the presence of 
iron very distinctly indicated, the use of a brown, and not 
a white, barytes may be suspected. 

Having determined the colouring-matters previously, 
a method to produce a match to the colour can easily be 
devised. 

The following examples will perhaps illustrate the pro- 
cedure better than more elaborate descriptions. 

A sample of orange lake to be matched gave a smooth 
bright lake, intermediate in shade between those produced 
from Orange II and Mandarin B, (Ber.). The lake, when 
incinerated, showed the presence of aluminium, a consider- 
able amount of barium sulphate and some clay. A trial 
was made with — 

56 parts clay. 



100 , 


alum, sulph. 17 per cent. 


35 , 


soda ash. 


40 , 


, Mandarin K. 


20 , 


, Orange II. 


156 , 


barium chloride. 



The shade produced was too red and too weak. The 

10 



146 THE MANUFACTURE OF LAKE PIGMENTS. 

clay was reduced to 28 parts, the Mandarin R to 30, 
and the Orange II increased to 30 parts ; the shade was 
approximately that required, but a little too full. On 
increasing the clay to 35 parts, the lake produced matched 
the sample exactly. 

Again, a maroon lake, much deeper in colour than any 
of the ordinary standards, rubbing out very smoothly, but 
deepening considerably on heating, gave a base similar 
to that described previously, but no possible combination 
with a blue shade of Ponceau, namely, Ponceau 4R (Ber.), 
gave the tone required. On heating the lake with a weak 
solution of sodium carbonate, a very dull, dirty magenta- 
coloured liquid was obtained. The addition of a brown 
colouring-matter, a proportion of Acid Brown B (Basle), 
to the Ponceau, gave a shade nearer to that required, but 
still not quite correct. By using a mixture of Bismarck 
brown and magenta the shade was finally determined. 

A bright scarlet lake, the base of which proved to be 
a mixture of blanc-fixe and aluminium hydrate, was much 
more red than Ponceau GL (Ber.), much brighter than 
Scarlet GR, and much yellower than Scarlet 3R (M. L. 
& B.) ; but was matched by a mixture of Scarlet 3R, 
Ponceau GL, and Orange II, after two trials made to 
determine the correct quantities. 



CHAPTEK XIV. 

SKETCH OF ORGANIC COMBINATIONS. 

The following short sketch of the combinations of the 
various hydrocarbons has been given, in order to illus- 
trate how such combinations occur, to render the con- 
stitutional formulae of the various colours more easily 
understood, and to enable the lake-maker to dissect the 
constitution of the colour, in order that he may not only 
apply the precipitating agent to the colour but convert it 
into a true lake. To enter into the theoretical considera- 
tion, and the modes of production of the various derivatives 
of the hydrocarbons of either the aromatic or fatty series, 
is beyond the scope of a text-book dealing with lake manu- 
facture ; for this, the reader is referred to some standard 
systematic work in organic chemistry. 

In organic chemistry the compounds are divided into 
two series, the fatty and the aromatic, or the derivatives 
of methane and benzene respectively. It is from the latter 
the dyestuffs are derived, but radicles of the methane series 
enter into the combinations as well as inorganic radicles, 
such as amido, hydroxy, azo, and sulphonic-acid groups. 

The carbon compounds of the methane series are 
the derivatives of a homologous series of hydrocarbons of 
which the simplest member is methane CH 4 ; and by the 
substitution of one of the hydrogen atoms in the latter by 
the methyl-radicle, a series of compounds of increasing 
complexity is derived. 

(147) 



1 18 THE MANUFACTURE OF LAKE PIGMENTS. 

(H H 

!h c |h 

e |H L -,H 

lH (CH, 

Methane. Ethane. 

A- the number of methyl-radicles increases, substitution 
can take place in more than one grouping, giving rise to 
isomers ; e.g., there are five isomers of hexane, namely — 

Normal hexane, CH 3 CHXHXHXHXH . 

Isohexane. CH 3 CHXHXH -j [S 

Tetramethvl-ethane, £5 ,N >HC— CK^^S 3 

Methyldiethyl-methane. GH 3 Ch/^.^ 3 

CH 3 

Trimethvlethvl-methane, H 3 C — C— CH.,XH 3 

I 
CH 3 

In colouring-matters these hydrocarbons and their 

compounds are chiefly met with as substituent groupings 

for hydrogen or some radicle, and the most important 

compounds of these hydrocarbons, simple and complex, 

may be roughly classified as — 

(' H \ 

The ethers or oxides of the radicle, such as ethyl ether r .--rT 5 /O 

^ 2-^-5/ 

or for the whole series, letting R represent the radicle -d ")0. 

The alcohols or hydroxides, for example, ethyl alcohol, T 2 H ; ,OH. 

or R— OH. 
The acids ; acetic acid may illustrate CH 3 X : OOH or RCOOH. 
The aldehydes ; the partially oxidized alcohols, for instance, 

acetic aldehyde, CH 3 - C^q or R — ^Cq 

The ketones ; oxidized secondary alcohols, e.g., acetone 

cl:> c °. « r>° 



SKETCH OF ORGANIC COMBINATIONS. L49 

These simple illustrations may be taken as representa- 
tive of the classes into which the compounds of the methyl 
series may be divided ; but it must be borne in mind that 
the substitution products and the derivatives of the higher 
members of the hydrocarbons form much more complex 
bodies than those outlined above. Glycerine is an alcohol 
of this series, but it is a trihydroxy body, C a H (OH) 3 . 

Oxalic and succinic acids are examples of more com- 
plex acids. Oxalic acid may be looked upon as acetic 
acid, in which the methyl-radicle has been oxidized to the 
carboxyl group — 

CH 3 C : O-O-H 

I I 

C : O-O-H, C : O-O-H 

Acetic acid. Oxalic acid. 
Succinic acid, C.,H 4 (COOH).,. The acids of this series have 
the general formula R(COOH).,. 

The simplest representative of the aromatic or benzene 
series is benzene, C 8 H 6l which is assumed to be represented 
by six carbon atoms combined to form a ring, each carbon 
atom being also combined with a hydrogen atom. Thus — 



H 

| 


H 

| 


H 

1 


H 
C 


C - 

II 
C - 

1 


- C 

- c 
1 


-O— o- 

II II 


HC/'XCH 

or, as usually written, 1 || 

HC ^v , CH 


H 


H 


H 


C 
H 



or more simply by || ; but the sign | , as a 

V \/ 

general rule, represents this hydrocarbon. 
The homologues of this series are formed by the substitution 
of the hydrogen, combined with one of the carbon atoms. 
by the 

/\ /\ 

methyl-radicle, e.g., toluene . xylene | CH :-. 



150 THE MANUFACTURE OF LAKE PIGMENTS. 

Reference to the formula of benzene will show, how- 
ever, that, in xylene, the methyl-radicle (CH 3 ), can be sub- 
stituted in the benzene ring, in three different positions 
with respect to each other. Without entering into a detailed 
account of the theory of this question, it is sufficient to 
note that the properties of a disubstitution product of ben- 
zene vary considerably, according to the position of the 
second substituent grouping. 

The three positions have been named the ortho-, meta-, 
and para-positions. 

The ortho-position is that in which the hydrogens are sub- 
stituted in two adjacent carbon atoms in the benzene ring, 
CH, 



e.g., oitho-xylene | 



The meta-position. The hydrogens substituted are separated 
by one intervening unsubstituted hydrogen; metaxylene 
CH q 



CH 3 

The para-position. Two unsubstituted hydrogens intervene 

CH, 

between the substituted hydrogens ; paraxylene 

CH g 

Naphthalene, C 10 H 8 , may be regarded as a condensation 

product of two benzene rings. 

8 1 

Thus— || || II generally 

5 4 
Benzene. Benzene. Naphthalene. 

1 




written It will be seen that there are eight 

'3 

5 4 



SKETCH OF ORGANIC COMBINATIONS. 151 

hydrogen atoms in this hydrocarbon, in which substitu- 
tion can take place. An examination of the formula 
shows that the hydrogen atoms may he divided into two 
groups, namely, 1:4:5:8 and 2:3:6:7. The several 
members of each group bear the same relations to each 
other, but differ from the members of the other group ; 
for 1 : 4 : 5 : 8 are linked to carbon atoms which are not 
combined with hydrogen, and 2:3:6:7 are linked as 
in an ordinary benzene ring. From this it can easily be 
surmised that, of the isomeric mono-substitution pro- 
ducts of naphthalene, two classes are known and have 
been isolated, viz., a and (3 substitution products. The 
alpha-substitution products are those in which the 
hydrogen in 1 : 4 : 5 or 8 is substituted, and the beta 
those in which the hydrogen in either 2 : 3 : 6 or 7 has 
been replaced — 

8 1 o o 

CO! 03 ICO! 

5 4 o o 

The multisubstitution products of naphthalene give 
rise to many isomers, but it is usual to indicate the 
position of the substituent groupings, when known, by 
numerals. Thus — 

Naphthalene disulphonic acid (2 : 6) 

HO ;i S N 

HO,S^ 
Naphthalene disulphonic acid (2 : 7) 




/ 



In like manner, anthracene, C U H 10 , may be considered 
as a condensation product of three benzene rings — 



H H H 

C C C C c 

I II 



0.0.0 KE 



\y v \s a ^\/ > r r \z 

Benzene. Benzene. Benzene. C ^ *~ l c'H 

H H 

Anthracene 



152 THE MANUFACTURE OF LAKE PIGMENTS. 

This hydrocarbon is used almost entirely for the pro- 
duction of alizarine' colours, and, since these have almost 
exclusively one general formation, it will not be of service 
to enter into the reactions of anthracene. 

The derivatives of benzene and naphthalene occur 
widely in combination with chromophors in colouring- 
matters, and, besides playing an important part in the 
colour molecule, it is chiefly to their reactions, and their 
influence that the lake-forming properties of the colours 
are due. It is therefore essential to survey briefly the 
more important derivatives. 

The monohydroxy derivatives : those in which one 
hydrogen atom of the hydrocarbon has been substituted 
by the hydroxy-radicle, (OH), which confers weak acid 
properties. The principal members of this group are — 

OH 

Phenol or carbolic acid 

o, CH 3 m. CH. p, CH. 
A°H A 
Ortho- meta- and para-cresol 

/V/\OH 



OH 




a, OH $ 

Alpha- and beta-naphthol j 

The primary amines : hydrocarbons in which one 
hydrogen atom has been replaced by the amido-radicle. 
(NHo), giving a distinctly basic nature to the compound, 
and causing it to combine readily with acids. Amido 
compounds when acted upon with nitrous acid (HNO.^ 
are converted into diazo compounds, e.g. — 

RNHgHCl + HXO., ; RN : NCI + 2H.,0 



SKETCH OF ORGANIC COMBINATIONS. 153 

Of this group the more important members are — 

NH„ 
Aniline 



The ortho- raeta- and para-toluidines- 



o, CH S m, 


CH 3 


p, CH ; 


/\NH 2 




(\ 


n 


\/NH 2 


y 






NH 2 


The xylidenes, amido 


-m. -xylene — 


CH, 

A 




CH, 

Anh., 


1 amido-] 


p. -xylene 


T , 


VCH 3 




V 


NH, 




CH :t 


CH S 






A CH * 






Cumidine 


, and 




H^vJ 






CH. 







a, NH, 0, 

Alpha- and beta-naphthylamine 



NH., 



The sulphonic acids are those substitution products in 
which one or more hydrogen atoms have been .replaced by 
the radicle (HS0 3 ) ; this gives distinctly acid properties, 
and the sulphonic acids readily combine with basic oxides, 
in many cases producing insoluble compounds. 

The chief members of this group are — 

Benzene monosulphonic acid, C i; H 5 SO a H 

S0 3 H S0 3 H 
/\ 
Meta- and para-benzene disulphonic acids | 

X^/SOjH 

S0 3 H 
Alpha- and beta-naphthalene monosulphonic acids 

a, S<>H 0, 




154 THE MANUFACTURE OF TAKE PIGMENTS. 

The naphthalene disulphonic acids, which are in some 
cases distinguished by the names of the discoverers — 

so 3 H 

Armstrong's 8-acid (1 : 5) 





S0 3 

SO,H 

■"CO 

/y\ SO3H 

HO,S/V^\SO.K 



S0 3 H 
" SO s H 

Ewer and Pick's acid (1:6) 

Armstrong's y-acid (1 : 7) 
Ebert and Merz's /8-acid (2 : 6) 

a-acid (2 : 7) 

The tri- and tetra-naphthalene sulphonic acids, 

Ci H 5 (SO 3 H) 3 , C 10 H 4 (SO 3 H) 4 . 
The Organic Acids. — The carboxyl or acid-forming 
radicle gives, with the hydrocarbons, true acids. It 

CH 3 

has been shown that the oxidation of ethane | results 

CH 3 

in the formation of acetic acid, CH 3 COOH, which may be 
regarded as methane, in which one of the hydrogens is sub- 
stituted by the carboxyl-radicle, (COOH). Thus the sub- 
stitution of hydrogen atoms in the aromatic hydrocarbons 
gives rise to distinct acids, of which the following are of 
most interest : — 

COOH 

Benzoic acid, I 

/\COOH 
Phthalic acid, orthobenzene dicarboxylic acid, j 

\yCOOH 

and its di- and tetra-halogen derivatives, C 6 BL,C1 2 <^ mnT r 
/COOH 
^ '' 4 \COOH 



SKETCH OF ORGANIC COMBINATIONS. 155 

The Nitro Compounds.— These are formed from the 
hydrocarbons by the substitution of the nitro-radicle (N0 2 ), 
for one or more hydrogen atoms, such substitution impart- 
ing acid properties to the compounds. The leading 
members of this series are: — 



NO, 
Nitrobenzene, C 6 H 5 N0 2 , | 



m.-dinitrobenzene, C (; H 4 (N0 2 ) 2 , ( 



NO., 



O. P. 

CH : , CH 3 



o.- and p.-nitrotoluene, C^CHgNO,, f | and I 

N0 2 
CH 3 
/\NOo 
Dinitrotoluene, C 6 H 4 CH 3 (NO,), 1:2:4, 



NO, 
CH 3 

Nitroxylol, C 6 H 3 (CH*) 2 N0 2 1:2:4 fj CHs 

N0. 2 
NO, 




tt-nitronaphthalene, C 10 H 7 NO 2 

NO, 
a-dinitronaphthalene, C 10 H t; NO, 

NO, 
The substitution products dealt with above have been 
chiefly the monosubstitution bodies, but substitution can 
take place in more than one position at the same time, and 
in the same molecule. Of the multisubstitution products 
in which the hydroxy-radicle occurs, the chief are — 

OH 
Resorcinol, C, ; H 4 (OH) 2 



../OH 



156 THE MANUFACTURE OF LAKE PIGMENTS. 

OH, 

Orcino^A {C H 4 , jl h 

OH 

OOH 

The dioxynaphthols, of which there are ten, C lft H 6 (OH) 2 : 
e.g.— 



OH 




01 

Among the amido multi-substitution products are found 
the diamines, and the secondary and tertiary amines. Of 
the diamines the principal members are — 

m, NH, p, NHo 
The phenylene diamines, 6 H 4 (NH 2 ) 3 



NH, 

The tolylene diamines, C 6 H 4 CH 3 (NH.,)., 
CH, CH 3 

(1:2: 4)/\NH, (1:2:5) /\NH 2 



)^NH 2 ( l;2:5) 

NhJJ 



NH 2 

With this class, the diamines in which substitution has 
already taken place in the amido-radical may be con- 
sidered ; e.g. — 

Diphenyl m.-phenylenediamine, CH,^™ tt 

4 JN MOj-xl- 

Diphenyl naphthylenediamine, C 10 H ^^^-> 

Diamido-diphenylamine, NH(C li H 4 NH.,)., 

C 6 H 4 NHa 

Benzidine, H„n/ N (~~ ~^NH 

C 6 H 4 NH, " V - 

C 6 H 3 CH 3 NH, GH S CH 3 

Toluidine, | NH./ > — ( >NH„ 

C,H 3 CH 3 NH, 



SKETCH OF OBGANIC COMBINATIONS. loT 

Among the secondary and tertiary amido-derivatives 
are found — 

H 
Diphenylamine, NH ^'^>, (^_)— n— <^} 

Benzylaniline, C H 5 NH . CH 2 . C.H^ <C_) NHCH 2<^ 

Dimethylaniline, N— CH 3 
\CH 3 

/H 

Monoethylaniline, N— CH^CH., 
\C 6 H, 



w ^ CH., 



Dimethyl-a-naphthylamine, C 10 H 7 N(CH 3 ) 2 

Phenyl-a-naphthylamine, C 10 H 7 NHC H.- 
NHCH-, 

a 

/\ CH— CH 
Quinoliue, C 9 H-N, | 

\y— N = CH 

/\C(CH„)CH 
Quinaldine, C 10 H 9 N, 

\y— N=CH 

C H 
Carbazol'.CjjjHjN, | b 4 ^>NH 

Orthomethyl benzidine, 

C 6 H 4 NH,(1:4) /-- 

C 6 H 3 (CH 3 )NH ( ' 6 ■ 4) 2 N /— \ ' 

C 6 H 3 NH L , 
Diamido carbazol, HN' 

\C H 3 NH L( 

p.-diamido stilbene. C'„H 4 (NH 2 )CH : CH-C H 4 NH. 
CH=HC 



CH, 

\ 
NH, 



NH 2 NH, 



158 THE MANUFACTURE OF LAKE PIGMENTS. 

The sulphonic acids of the amido- and hydroxy- 
derivatives are of the utmost importance, being of frequent 
occurrence in the molecules of colouring-matters . The chief 
phenol-sulphonic acids are — 

p, OH o, OH 

y\ /\so,h 
o. and p.-phenol sulphonic acid, C^H^SOaHOH 

S0 3 H 

SO TT 
The a-naphthol monosulphonic acids, C 10 H 6 -.-p| , of 

which there are several isomers, but the most important 

OH 

is a naphthol monosulphonic acid. N\V, 1 : 4 | 

so: f H 

The a-naphthol disulphonic acids, C 10 H-k-rT • i '' 2 , of which 

of the many isomers (1:2: 1) 

OH OH 

SO,H H0 3 S/V/\SO..H 

and (1:2:7) are the principal 

SO.H 

The a-naphthol tiisulphonic acids, of which the following 

two are the most common : — 

OH 
H0 3 S/V/\S0 3 H 
a-naphthol trisulphonic acid, 1:2:4:7 

SOaH 
SOjH OH 






a-naphthol trisulphonic acid, 1:3:6:8 

The /3-naphthol monosulphonic acids, four of which 
are generally in use, namely — 

S0 3 H 

OH /V\.° H 

Bayer's acid, C 10 H 6go H (2 : 8) 

Schaffer's acid, C 10 H, ; oq tt(2 : 6) 



SKETCH OF ORGANIC COMBINATIONS. 159 

Dahl's acid, C 10 H g^ H (2 : 5) f Y j 

SO^H 
q H S0 3 H/\/\OH 

Cassella's acid, C 10 H gQ -^(2 : 7) 

The /3-naphthol disulphonic acids. Of the many 
isomers, the following are of most importance — 

/3-naphthol disulphonic acid, C 10 H 5 OH(SO 3 H) o 2:3:6 

rn oH 

HOaS^/VSOsH 

/3-naphthol disulphonic acid, C 10 H 5 OH(SO 3 H) 2 (2:6:8) 

HO..S 

sOH 




HO.^ 
/3-naphthol trisulphonic acid, C 10 H 4 OH(SO 3 H) 3 , most 

HO,S 

/\/\OH 
probably 2:3:6:8 

HO,S l N/ > N /S0 3 H 

The sulphonic acids of the dioxynaphthalenes are im- 
portant derivatives of this group, and give rise to many 
isomers ; those in use are believed to be various mixtures 
whose exact constitutions are unknown. 

The amido-sulphonic acids are of equal importance with 

the hydroxy-sulphonic acids. The principal members of 

use in lake manufacture are — 

P , NH 2 m, NH 2 

The sulphanilic acids, C (5 H 4 NH 2 S0 3 H 



;so 3 H 
SO.H 

Phenylhydvazine p. -sulphonic acid, CuH^NHNHoSOjH 

NHNHo 



S0 3 H 
The toluidine sulphonic acids, C H 3 (CH 3 )(NH 2 )SO 3 H 
The xylidine sulphonic acids, C 6 H 2 (CH 3 ) 2 (NH 2 )S0 3 H 



160 THE MANUFACTURE OF LAKE PIGMENTS. 

The a-naphthylamine sulphonic acids, C 10 H G NH 2 SO 3 H, of 
the seven isomers of which (1 : 4), (1 : 3), (1 : 6), (1 : 8), 
and (1 : 2) occur most frequently in colour molecules. 

a-naphthylamine sulphonic acid 

NH, NH., 



1: *UU (1:6) WUJ etc - 

S0 3 H 

The a-naphthylamine disulphonic acids and trisulphonic 
acids. The following of the many isomers will serve to 
illustrate their constitution — 

a-naphthylamine disulphonic acid, C 10 H 5 NH 2 (SO 3 H) 2 
HO :! S NH, 

1:3:8 




a-naphthylamine trisulphonic acid, C 10 H 4 NH 2 (SO 3 H) 3 

NH 2 
HO.,S^V\SO,H 
(1:,2:4:7) 

S0 3 H 

The /3-naphthylamine mono-, di-, and trisulphonic acids 
are equally important with those of a-naphthylamine, and 
their constitution is similar, save that the amido group is 
in the /3-position. 

Eeferring to the sulphonic acids of the diamines, and 
the secondary and tertiary amines, the following are of 
importance : — 

Methyl and ethyl ^3-naphthylamine sulphonic acid, 
C 10 H 6 SO 8 HNHCH 3 and C 10 H 6 SO 3 HNHCH 2 CH 3 
Diamido-naphthalene disulphonic acids, 
C lfl H 4 (NH 2 ) 2 (S0 3 H) 2 

NH., NH 2 NH 2 

HO,S/V\ /V\ 

1:5.3:7 and (1 : 8 : 3 : 6) 

^A^ S0 - H H0 3 S 1 N / s/ SO,H 

NH„ 



SKETCH OF ORGANIC COMBINATIONS. 161 

The amido-phenols, that is, those compounds in which 
both the hydroxy- and the amido-radicles occur, may be 
illustrated by — 

m, NH 2 

w-Amido-phenol, C 6 H 4 NH.,OH [ \ 
and derivatives such as dimethyl-amido-phenol, C (i H 4 <^ ~4r 3 ' 2 ' 

and diethyl-amido-phenol, C t; H 4 ^ ^L- - 5 ' 2 , from which are 

/NO 
derived nitroso compounds similar to C,H 3 — OH 

\N(CH 3 ) 2 

Of the amido-naphthols several are largely used in the 
preparation of azo colours. A type may be expressed in 
this manner : — 

NH 2 

C 10 H (i OHNH 2 (l : 2) QQ* 

The amido-naphthols give rise to a series of mono-, di-, 
and trisulphonic acids, which are of great importance in 
the production of the above-mentioned azo-colours. There 
are many isomers ; they may be written thus : — 

The monosulphonic acids, C 1() H 3 NH 2 OHS0 3 H(2 : 3 : 7) 
HCS/VNNHj 

JoH 

The disulphonic acids, C 10 H 4 NH 2 OH(SO 3 H) 2 (2 : 3 : 6 : 8) 

SO,H 

vANH, 



Among the derivatives of the amido-phenols may be 
counted anisidine, the methyl ether of amido-phenol, 



OCH 
C..H /?3 ' 



11 



162 THE MANUFACTURE OF LAKE PIGMENTS. 

and dianisidine, 

C, ; H 3 (OCH 3 )NH 2 

I 
C 6 H 3 (OCH 3 )NH 2 

The amido-nitro compounds are of considerable im- 
portance: — 

m, NH 2 p, NH, 

The nitranilines, C 6 H 4 NH 2 N0 2 , 



N0 2 
CH S 

The nitrotoluidines, C-H 6 NH 2 N0 2 , } 

\y 
no s 

Of the multisubstitution products containing the car- 
boxyl-radicle, COOH, and its derivatives, the following 
are some of the best examples : — 

Amido-benzoic acid, C 6 H 4 NH 2 COOH 

o, NH„ m, NH S 

\COOH 



/OOOH 

o, OH 

/\COOH 
Salicylic acid, C 6 H 4 (OH)COOH 

Amido-salicylic acid, C 6 H 3 (OH)(NH 2 )COOH 
Cresolic acids, C H 3 (CH 3 )(OH)COOH 
Gallic acid, trioxybenzoic acid, C 6 H 2 (OH) 3 COOH 
OH 

(V 

HOOC^OH 

OH 

O^COOH 

The introduction of the oxidation products of thefatty 
hydrocarbons, the aldehydes, ketones, etc., gives rise to 
a series of compounds, of which those of the greatest 
importance are : — 



SKETCH OF ORGANIC COMBINATIONS. 163 

H— C = 
Benzaldehyde, C H 5 CHO, and its derivatives, mono- 
arid dichlorbenzaldehyde, C H 4 C1CHO 

H— C = H— C = 

QC1 

The following hydroxy, nitro, and amido derivatives are 
of considerable interest : — 

p, NO, 
The nitro-benzaldehydes, C 6 H 4 (N0 2 )CHO 

CHO 
m, NH 2 

The amido-benzaldehydes, C 6 H 4 (NH 2 )CHO 



JCHO 
p, OH 

The oxybenzaldehydes, C 6 H 4 (OH)CHO 

CfiO 



Of the ketones the following are of interest : — 

K— C— E 

Benzophenone, C H 5 -C : 0*C 6 H 5 , and its derivatives the 
Amido-benzo phenones, C 6 H 5 -C : (>C 6 H 4 NH 2 


<Z>-c-<Z> H * 

The diamido-benzo phenones, C (j H t NH 2 -C : O-C H 4 NH 2 

H 

The oxidation of anthracene, C 14 H 10 j | gives 

H 
rise to anthraquinone from which alizarine colours are 
derived. 



164 THE MANUFACTURE OF LAKE PIGMENTS. 

Anthraquinone, C 12 H s (CO) 2 or 

O 



c « h <c8>a ° r O-o-O 



THE END. 



INDEX. 



Absorption of colouring matters by 

starch, 73. 
Acid, arsenious, 48. 

— — lake of magenta, 87. 
lakes, 77. 

— brown, B, 101, 146. 

colours, 101, 143. 

G, 16. 

R, 13. 

— colours, 72. 

carboxy group of, 81. 

hydroxy group of, 80. 

sulphonic group of, 82. 

lake-forming bodies for, 35. 

— — nitro group of, 80. 
sulpho group of, 81. 

— green colours, 21, 104. 

— — D, complete precipitation of, 

75. 

— oleic, action of, in lake formation 

from hydroxy colours, 80. 

— phosphoric, 47, 67. 

action of salts of, in lake pre- 
cipitation, 49. 

use with aluminium hydrate 

bases, 71. 

— picric, 9. 

— resinic, use in lake precipitation, 

50. 

— rosolic, 23. • 

— scarlet, 124. 

— stannic, use in lake precipitation, 

49. 

— tannic, 46, 83. 

lake of magenta, 77. 

lakes of basic colours, 77. 

— yellow colours, 102. 
D, 12. 

Acids naphthol-sulphonic, 158. 
Acridine colours, 26. 
Alizarine blue, 19. 

— Bordeaux, 19. 

— indigo blue, 19. 

— lakes, 42, 54, 118, 126. 



Alizarine lakes, identification of, 141. 
preparation of, 19, 95. 

— orange, 19, 100. 

— KG, 18. 

— S, 82. 

— VI, 18. 

— WS, 19. 
Alizarines, 18, 80. 
Alkali blue, 80, 143. 

— — D, 22, 106. 
Aluminium acetate, 42. 

— arsenite, 56. 

— hydrate, 43, 56, 63, 80. 

— resinate lake of safranine, 89. 

— salts of arsenious acid, uses of, 

66, 68. 

— — — phosphoric acid, uses of, 

66, 68. 

— sulphate, 41. 
Amido azo colours, 12. 

— compounds of the aromatic series, 

156. 

— naphthols, 161. 

— phenols, 161. 

— sulphonic acid colours, 101. 

acids, 159. 

Antimony oxide, 40. 
Aromatic aldehydes, 163. 

— carboxylic acids, 162. 

— ketones, 163. 

— nitro compounds, 155. 

— series of organic compounds, 149. 
Arsenious acid, 48. 

— acid lake of magenta, 87. 
lakes, 77. 

Artificial colours, azo group of, 10. 

— — classification of, 5. 

commercial forms of, 29. 

diluents of, "-".'. 

— — drying of lakes from, 124. 
fastness to light of lakes from, 

121. 

— — manipulation of, 29. 

— — nature of, 29. 



165 



166 



THE MANUFACTURE OF LAKE PIGMENTS. 



Artificial colours, nitro group of, 9. 

preparation of solutions of, 

33. 
properties of lakes from, 118. 

— — staining power of lakes from, 

120. 
Auramine, 20, 102, 138, 141. 

— effect of boiling solution of, 33. 

— precipitation of, 20. 
Aurine, 23. 

Auxochrome, definition, 6. 
Azine colours, 24, 26, 88. 
Azo benzene, 11. 

— colours, 10, 27, 86, 89 

fastness to ligbt of green lakes 

from, 121. 

of scarlet lakes from, 

121. 

insoluble, production of, 110. 

— diazo colours, 91. 

— pigment colours, 84, 100. 

— sulphonic acid colours, 100. 
Azophor red colours, 111. 
Azure blues, 61. 

Barium chloride, 13, 35. 

— hydrate, 84. 

— phosphate, 68. 

— sulphate, 55, 56, 69. 
Baryta, caustic, 36. 
Barytes, 8, 55, 56 

Base for hydroxy sulphonic acid 

colours, 91. 
Bases for lake colours, 52. 
classification of, 55. 

— lake, examination of, 144. 
Basic acetates of lead, 37. 

— colours, 72, 86. 

identification of blue lakes 

from, 143. 

lake formation from, 76. 

forming bodies for, 46. 

— green colours, 104. 

— violet colours, 67. 

— yellow colours, 102. 
Basle blue R, 26. 
Benzidine, 16, 91. 
Benzopurpurine 4B, 17. 
Berry yellow, 1. 
Biebrich scarlet, 16. 

Bismarck brown, 13, 92, 101, 120, 

143. 
Black, diamine, colours, 108. 

— F.H.A., Basle, 109 

— lakes, 108. 

identification of, 143. 

— lamp-, 61. 



Black, naphthol, 6B, 16. 

— vegetable, 56, 61. 
Blanc-fixe, 55. 

eosine lake on, 93. 

Bleeding of lakes, 123. 
Blue, alizarine, 19. 

— alkali, 80, 143. 
D, 22, 106. 

— Basle, 143. 
E, 26. 

— Chinese, 1, 80. 

— diphenylamine, 106. 

— fast, 2B, 25. 

— indigo, alizarine, 19. 

— lake colours, 105. 

— lakes, 105, 143. 

for lithographic work, 107. 

from basic colours, identifi- 
cation of, 143. 

— methyl, C, 22. 

— methylene, 26, 143. 

B, 25, 105. 

new, 25. 

— naphthalene, E, 105. 

— neutral, 106. 

— new, 143. 

— night, 22. 

— Nile, 105, 121, 143. 
A. 25, 105. 

lakes, fastness to light of, 

121. 

— patent, B.N, 106. 

— Prussian, 84 

— Victoria, 80, 105. 

— water, 143. 

— xylene, 106. 
Blues, azure, 61. 

— Chinese, 1, 80. 

— erioglaucine, 106. 

— patent, 6] . 
Bluish-red lakes, 87. 
Bordeaux, alizarine, 19. 

— B, 15. 

— G, 16. 

Bright purple lakes, 88. 
Brilliant green, 21, 104. 

— orange, O, 101. 
E, 101. 

— oranges, 140. 
Brown, acid, B, 101, 146. 

colours, 101, 143. 

G, 16. 

E, 13. 

— Bismarck, 13, 92, 101, 120, 143. 

— cloth, G, 17. 

— lakes, identification of, 143. 

— — preparation of, 101. 



INDEX. 



107 



Calcium acetate, 44. 

— carbonate, 61. 

— nitrate, 44. 

— phosphate, 68. 

— salts, purification of, 44. 

— sulphate, 59. 

Calico printing, rhodamine lakes for, 
87. 

Carboxy group of acid colours, 81. 

Carboxylic acids, aromatic, 102. 

Cardinal lakes, effect of sunlight on, 
1'22. 

Castor oil, sulphonated, 51, 57. 

Caustic baryta, 36. 

Ciba Red, 89. 

Chalk, 61. 

China clay, 58. 

Chinese blues, 1, 80. 

Chromates, lead, 1, 102. 

Chrome, violet, 23. 

Chromogen, definition, 6. 

Chrysoidine, 12. 

Classification of artificial colours, 
5. 

— — lake bases, 55. 

scarlet, red, and crimson lakes, 

140. 

Clay, absorption of colouring-matters 
by, 73. 

Cloth, brown, G, 17. 

Coccinines, 14. 

Cochineal, 1. 
Coeruleine, 24, 95, 104. 
Colophony, 50. 

Colouring-matters in lakes, esamina- 
tion of, 135. 

testing fastness to bleeding of 

136. 

light of, 136. 

Colours, acid, 72. 

brown, 101. 

carboxy group of, 81. 

green, 104. 

hydroxy group of, 80. 

lake forming bodies for, 35. 

nitro group of, 80. 

preparation of blue lakes from 

106. 

sulpho group of, 81. 

yellow, 102. 

— acridine, 26. 

— amido-azo, 12. 

— amido-sulphonic acid, 101. 

— artificial, azo group of, 10. 

classification of, 5. 

commercial forms of, 29. 

diluents of, 29. 



Colours, artificial, drying of lakes pre- 
pared from, 12 J. 

fastness to light of lakes from, 

121. 

— — manipulation of, 29. 

nature of, 29. 

nitro group of, 9. 

preparation of solutions of, 33. 

properties of lakes from, 118. 

staining power of lakes from. 

120. 

— azine, 88. 

— azo, 10, 27, 86, 89. 
diazo, HI. 

— azophor red, 111. 

— azo pigment, 84, 100. 
sulphonic, 100. 

— basic, 72, 76. 
green, 104. 

identification of blue lakes 

from, 143. 
yellow, 102. 

— commercial forms of dry lake, 132.. 

— compound, 75. 

— diamine black, 108. 

— blue lake, 105. 

— hydroxy, 93. 

sulphonic acid, 82, 91. 

— indoanthene, 27. 

— insoluble azo, production of, 110. 

— oxy-azo, 13. 

— oxyketone, 18, 95. 

— paste, 30. 

— pigment, 89. 

— — yellow, 102. 

— pulp, 58, 66, 122, 132. 

— quinoline, 26. 

— sulpho, 27. 

— triphenylamine, 20, 93. 

— triphenylmethane, 93. 
Compound colours, 75. 
Compounds of methane, 6. 
Crimson lake, 1. 

— lakes, effect of sunlight on, 122. 

identification of, 140. 

Croeeine scarlet BX, 15. 



Definition of auxochrome, 6. 

— — chromogen, 6. 
chromophor, 6. 

— — lake colour, 1. 

salt-forming group, 6. 

Diamine black colours, 108. 

— fast red, 17. 
Diamond green, 104. 
Diazoanisol, 14. 
Diluents of artificial colours, 29. 



168 



THE MANUFACTURE OF LAKE PIGMENTS. 



Diphenylamine blue, 106. 

— orange, 12. 

Disodium hydrogen phosphate, 47. 
Dry lake colours, commercial forms 

of, 132. 
Du.ch pink, 1. 
Dyes, eosine, 3. 
Dyestuffs, natural, 1. 

Earth, green, 54, 62, 104. 

— white, 54. 

Effect of heat on the shade of lakes, 

124. 
medium on fastness to light of 

lakes, 121. 

sunlight on crimson lakes, 122. 

— magenta lakes, 122. 

— — — — maroon lakes, 122. 
— orange lakes, 122. 

— — scarlet lakes, 122. 

— — violet lakes, 122. 

— — yellow lakes, 122. 

Emerald green, 1. 

Enamel white, 58. 
Eosine A, 23, 95. 

— GBF, 95. 

— dyes, 3, 23, 80, 88, 93. 

— lake on blane-fixe, 93. 

— lakes, fastness to light of, 121. 
identification of, 140. 

— — preparation of, 94. 

— yellowish, 93. 
Erioglaucine A, 107. 

— blues, 106. 
Erioglaucines, 41, 61. 

— identification of blue lakes from, 

143. 
Erythrosines, 24, 94. 
Ethyl green crystals, 49. 

— — lakes, fastness to light of, 121 

— — preparation of lakes from, 104. 
Examination of colouring-matters in 

lakes, 135. 

Fast blue, 2B, 25. 

Fastness to light of eosine lakes, 121. 

■ — ethyl green lakes, 121. 

green lakes, from azo 

colours, 121. 

— lakes from artificial col- 
ours, 121. 

— — — ■ — methvl green lakes, 121. 

Nile blue lakes, 121. 

— — orange II lake, 121. 

— — — — safranine lakes, 121. 

— — — — scarlet lakes irom azo 

colours, 121. 



Fast red B, 15. 

— — diamine, 17. 

— — helio, BL, 61, 112, 119. 

lakes, identification of, 141. 

O, 90, 92. 

Filtration of lakes, 130. 
Flavin, 1. 
Fustic, 1. 

Gambixe, 18. 
Galleine, 34, 95. 
Green, acid, 21. 

— brilliant, 21. 104. 

— colours, acid, 104. 
basic, 104. 

— crystals, ethyl, 49. 

— D, acid, 75. 

— diamond, 104. 

— earth. 54, 02, 104 

— emerald, 1. 

— ethyl, 104. 

— guinea, B, 21. 

— lakes, 95, 124. 

effect of sunlight on, 122. 

— — ethyl, fastness to light of, 121. 
preparation of, 103. 

— malachite, 21, 54, 104, 170. 
Green's method of dyeing ii. grain 

colours, 110. 
Guinea green B, 21. 
Gypsum, 59. 

Helio fast red EL, 61, 112, 119. 
Hydrazides, 20. 
Hydroxy colours, 93. 

— compounds of the aromatic series, 

155. 

— group of acid colours, 80. 

— sulphonic acid colours, 82. 

Identification of alizarine lakes, 141. 

black lakes, 143. 

blue lakes from basic colours, 

143. 

— — ■ — ■ — — erioglaucines, 143. 

— — brown lakes, 143. 

— — crimson lakes, 140. 

— — eosine lakes, 140. 

fast red lakes, 141. 

magenta lakes, 142. 

— — maroon lakes, 142. 

— — orange lakes, 139. 

— — permanent red lakes, 141. 
red lakes, 140. 

rhodamine, lakes, 142. 

— — s.ifranine lakes, 142. 
- — — scarlet lakes, 140. 



INDEX. 



169 



Identification of violet lakes, 142. 

yellow lakes, L38. 

Indigo blue, alizarine, L9. 

Incloanthene colours, 27. 

Indolines, 26, L06, L09. 

Inks, stencil, 28, 89. 

Insoluble azo colours, production of, 

110. 
Iso-nitroso and nitroso colours, 18. 

Kaolin, 58. 
Ketonimides, 20. 
Kieselguhr, 62. 

Lake bases, 7, 52. 

classification of, 55. 

— — examination of, 144. 

— blue, colours, 105. 

— — for lithographic work, 107. 

— colour, definition, 1. 

— colours, dry, commercial forms of, 

132. 

— crimson, 1. 

— formation, principles of, 72. 

— forming bodies for acid colours, 35. 
■ basic colours, 4(3. 

— — reagents, 7. 

— leather, 1. 

— madder, 1. 

— manufacture, practical details of, 

126. 

— maroon, example of matching, 146. 

— of magenta, tannic acid, 77. 

— orange, example of matching, 145. 
II, fastness to light of, 121. 

— pigments, matching, 134. 
testing, 134. 

— rose, 1. 

— scarlet, example of matching, 146. 
Lakes, alizarine, 42, 54, 118, 120. 
identification of, 141. 

preparation of, 95. 

— black, 108. 

— — identification of, 143. 

— bleeding of, 123. 

— blue, 105, 143. 

— bluish-red, 87. 

— bright purple, 88. 

— brown, identification of, 143. 

— — preparation of, 101. 

— cardinal, effect of sunlight on, 122. 

— crimson, effect of sunlight on, 122. 
identification of, 140. 

— effect of heat on the shade of, 124. 

— eosine, fastness to light of, 121. 

identification of, 140. 

preparation of, 94. 



Lakes, ethyl green, fastness to light 

of, 121. 
— preparation of, 104. 

— fast red, identification of, 141. 

— filtration of, 130. 

— final treatment in manufacture of, 

132. 

— for surface paper work, ss. 

— from artificial colours, drying, 124. 

— fastness to light of, 121. 

properties of, 118. 

staining power of, 120. 

— green, 95, 124. 

effect of sunlight on, 122. 

from azo colours, fastness to 

light of, 121. 
preparation of, 103. 

— magenta, effect of sunlight on, 122. 

— — identification of, 142. 

— — maroon, action of heat on, 124. 

— maroon, 112. 

effect of sunlight on, 122. 

identification of, 142. 

— methyl green, fastness to light of, 
* 121. 

— Nile blue, fastness to light of, 121. 
— ■ orange, effect of sunlight on, 122. 
identification of, 139. 

preparation of, 100. 

— permanent red, identification of, 

141. 

— Ponceau, action of heat on, 124. 

— — matching of, 141. 

— practical details of washing of, 

128. 

— red, 86. 

• — — identification of, 140. 
scarlet, and crimson, classifi- 
cation of, 140. 

— reddish-pink, 87. 

— rhodamine, for calico printing, 87. 
identification of, 142. 

— safranine, fastness to light of, 121. 
identification of, 142. 

— scarlet, effect of sunlight on, 122. 

— — from azo colours, fastness to 

light of, 121. 

— — identification of, 140. 
matching, 141. 

— testing the staining power of, 122. 

— violet, 67, 88. 

— — effect of sunlight on, 122. 

identification of, 142. 

preparation of, 108. 

tinting of, 88. 

— yellow, effect of BOnlight on, 122. 

— — identification of, 138. 



11 



170 



THE MANUFACTURE OF LAKE PIGMENTS. 



Lainp-blac-k. 61. 
Lead ac tati . 37. 

— — basic, 37. 

— " bottoms," 60. 

— chromates, 1, 102. 

— nitrate, 37. 

— orange, 60. 

— phosphat.. 68. 

— salts as lake precipitants, 38. 

— sulphate, 60. 

— white, 60. 
Leather lake, 1. 
Lima wood, 1. 
Linoleum pigments, 8. 
Lithographic pigments, 8. 
Lithol reds, 3, 112. 
Lithopone, 61, 132. 
Logwood, 1, 108. 

Madder lake, 1. 
Magenta, 22, 92. 121, 146. 

— arsenious acid lake of, 87. 

— lakes, effect of sunlight on, 122. 
identification of, 142. 

— maroon lakes, action of heat on, 

124. 

— tannic acid lake of, 74, 77. 
Malachite green, 21, 54, 104, 120. 
Mandarin G, 101, 140. 

— GR, 14. 

— R, 101, 140. 

Manipulation of artificial colours, 29. 
Maroon lakes, 92. 

— — effect of sunlight on, 122. 

example of matching, 146. 

identification of, 142. 

Matching lake pigments, 134. 
Metanil yellow, 13, 102, 138. 
Methane compounds, 6, 147. 
Methyl blue C, 22. 

Methyl green lakes, fastness to light 
of, 121. 

— "violet, 142. 
B, 88. 

— production of pale alumin- 
ium lake from, 42. 
Methylene blue, 26, 143. 
B, 25, 105. 

— — new, 25. 
Minium, 60. 

Naphthalene blue R, 105. 
Naphthol black, 6B, 16. 

— green S, 103. 

— sulphonic acids, 158. 

— yellow, 9, 103. 

— — S, 9, 102, 138. 



Natural dyestuffs, 1. 

— pigments, 1. 

Nature of artificial colours, 29. 
Neutral blue. 106. 
New blue. 143. 

— methylene bhi' 
Night blue, 22. 

Nile blue, 105, 121, 143. 

A. 25. 105. 

lakes, fastness to light of, 121. 

Nitro alizarine, 100. 

— compounds of the aromatic series, 

155. 

— group of acid colours, 80. 

artificial colours, 9. 

Nitroso and iso-nitroso colours, 18. 

Ochre, 1. 

Oil, sulphonated castor, 51, 57. 

Oleic acid, action of, in lake formation 

from hydroxy colours, 80. 
Orange, alizarine, 19, 100. 

— diphenylamine, 12. 

— lakes, effect of sunli-ht on, 122. 

— — example of matching, 145. 
identirication of, 139. 

— — preparation of, 100. 

— lead, 60. 

— O, brilliant, 101. 

— R. brilliant, 101. 

— II, 14, 101, 140. 

lake, fastness toilight of, 121. 

Oranges, brilliant, 140. 
Oxazines, 24. 
Oxide of antimony, 40. 
Oxy-azo colours, 13. 
Oxyketone colours, 18, 95. 

Parasite aniline red, 112, 115. 
Pararosaniline, 22. 
Paris white, 59. 
Paste colours, 30. 
Patent blue BN, 106. 

— blues, 61. 

Permanent red lakes, identification 
of, 141. 

— reds, 3. 

— white, 58. 

Phenol sulphonic acids, 158. 
Phloxines, 24, 94. 
Phosphines, 27, 100. 
Phosphoric acid, 47, 67. 
action of salts of, in lake pre- 
cipitation, 49. 
Phthelein dyestuffs, 23. 
Picric acid, 9. 
Pigment colours, 89. 



INDEX. 



171 



Pigment yellow colours, 102. 
Pigments, linoleum, 8. 

— lithographi 

— natural, 1. 
Ponceau 2G, 15. 

— 4GBL, 90. 

— GI., 'Jo. 

— (ill, 90. 

— lakes, matching, 141. 

— 2B, L5. 

— 3B, 1",. 

— 4i;, '.in. 

— 4KB, 16. 

— 4RB, action of heat on lakes pre- 

pared from, \'2A. 
Practical details of lake manufacture, 
126. 

— lake washing, 128. 

Precipitation of auramine, 20. 
Preparation of alizarine lakes, 19, 
95. 

blue lakes for lithographic 

work, 107. 

— — eosine lakes, 94. 
ethyl green lakes, 104. 

— — green lakes, 103. 

— — orange lakes, 100. 

paranitraniline red, 115. 

solutions of artificial colours, 

33. 

violet lakes, 108. 

Primuline, 17. 

Principles of lake formation, 72. 

Production of insoluble azo colours, 

110. 
Properties of lakes from artificial 

colours, 118. 
Prussian blue, 84. 
Pulp colours, 58, 66, 122, 132. 
Purification of calcium salts, 44. 
Purple lakes, bright, 88. 
Purpurin, 19. 

Quinoline colours, 26. 

— yellow, 27, 102, 138. 

Red, Ciba, 89. 

— fast, B, 15. 

diamine, 17. 

O, 90, 92. 

— helio fast, EL, 61, 112, 119. 

— lakes, 86. 

fast, identification of, 141. 

identification of, 140. 

permanent, identification of, 

141. 

— paranitraniline, 112, 115. 



Red, Bcarlel 1 crimson lakes, classi- 
fication of, 140. 
Reddish-pink la kes, 87. 
Reds, lithol, 3, 112. 

— permanent, 3. 
Resmic acid, 50. 
Resorcin yellow, 14. 
Rhodamine B, 24, 87. 

— G, 87. 

— 6G, 87. 

— 12G, 87. 

— lakes for calico printing, 87. 
identification of, 142. 

— S, 24, >7. 
Rhodamines, 23. 
llosaniline dyestuft's, 21. 
Rose Bengal, 24, 94. 

— lake, 1. 
Rosin, 50. 
Rosolic acid, 23. 

Safraxlne lakes, fastness to light, 
121. 

identification of, 142. 

Safranines, 25, 88, 92, 108. 
Salt-forming group, definition, 6. 
Sapan wood, 1. 
Satin white, 59. 
Scarlet, acid, 124. 

— croceine BX, 15. 

— lake, example of matching, 146. 

— lakes, effect of sunlight on, 122. 

— — from azo colours, fastness to 

light of, 121. 

identification of, 140. 

matching, 141. 

— 3R, 90. 

— red and crimson lakes, classifica- 

tion of, 140. 
Sodium acetate, 45. 

— phosphate, 47. 

Staining power of lakes from artificial 
colours, 120. 

testing, 122. 

Stannic acid, 49. 

— chloride, 50. 
Stannous chloride, 44, 50. 

Starch, absorption of colouring-mat- 
ters by, 73. 
Stencil inks, 28, 89. 
Sulpho colours, 27. 

— group of acid colours, 81. 
Sulphonated castor oil, 51, 57. 
Surface paper work, lakes for, 88. 

Table of lake bases, 55. 
Tannic acid, 46, 83. 



172 



THE MAXCFACTURE OF LAKE PIGMENTS. 



Tannic acid lakes of basic colours, 
77. 

■ lake of magenta, 77. 

Tartar emetic, 40. 
Tartrazine, 20, 102 
Testing fastness to bleeding of colour- 
ing matters, 136. 

— light of colouring-matters. 

136. 

— lake pigments, 134. 

— the staining power of lakes, 122. 
Tetrazo benzene phenol, 16. 

— dyestuffa, 15. 
Thioazines, 24. 
Thionavine T, 102, 138. 
Tin printing, 89. 
Tinting of violet lakes, 88. 
Triphenylamine colours, 20, 93. 
Triphenvlmethane colours, 93. 
Tropaolin O, 14. 

— 00, 4. 

Vacuum filter for filtration of lakes, 

130 
Vegetable black, 56, 61. 
Victoria blue, 80, 105. 
Violet basic colours, 67. 

— chrome, 23. 

— lakes, 67, 88. 

effect of sunlight on, 122. 

identification of, 142. 



Violet lakes, preparation of, 108 

— — tinting of, 88. 

— methvl, 142. 
B,* 88. 

Water blue, 143. 

Weld, 1. 

White earth, 54. 

— enamel, 58. 

— lead, 60. 

— permanent, 58 

— zinc, 60 
Witherite, 36 

Xylene blue, 106. 

— yellow, 103. 

Yellow colours, acid, 102. 
basic, 1(12. 

— — pigment, 102. 

— lakes, effect of sunlight on, 122 
identification of, 138. 

— metanil, 13, 102, 138 

— quinoline, 27, 102, 138. 

— naphthol, 9. 

— S, naphthol, 9, 102, 138. 

— resorcin, 14. 

— xylene, 103. 

Zixc sulphate, 40. 

— white, 60. 



ABERDEEN : THE UNIVERSITY PRESS 



Wxm 



mm 
mm® 



fomL 



.•■•■■■■■•■ 

• .■•..,■''■■. 



mmMm 








wHHHHf 



Han